JPH08227204A - Electrifying member and electrifying device - Google Patents

Abstract

PURPOSE: To reduce electrical contact among the fibers of an electrifying brush and to enable uniform electrification by providing a conductive core member electrically connected to a substrate and a coating layer having volume resistivity, etc., higher than that of the core member in the electrifying brush. CONSTITUTION: A DC electrifying bias of -1200V is applied to the electrode 2a of a rotary electrifying brush 2 in contact with a photoreceptor 1 from a power source S1 for applying an electrifying bias, to uniformly electrify the outer periphery of the photoreceptor 1 to about -680V by discharging. The electrifying brush 2 is constituted as a roll brush in such a manner that a sheet obtained by electrostatically flocked dual pipe construction conductive fibers provided with a resistance coating film 2d having >=10<10> Ωcm volume resistivity on a conductive nylon inner needle (core member) 2c having <=10<7> Ωcm volume resistivity, on the conductive polycarbonate substrate 2b having 10<4> Ωcm volume resistivity is wound. The dual pipe construction electrifying brush 2 is used to prevent the electrical contact among the fibers of the brush and enable the uniform electrification.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member and a charging device for charging (including destaticizing) an object to be charged. More specifically, the present invention relates to a contact type charging device that charges a charged member by bringing a charging member to which a voltage is applied into contact with the charged member.

The charging device preferably performs an image formation by applying an image forming process including a step of charging a charging member applied with a voltage to the image carrier to charge the image carrier. It is applied to image forming devices such as photocopiers and electrostatic recording copiers and printers.

[0003]

2. Description of the Related Art Conventionally, in an electrophotographic type or electrostatic recording type image forming apparatus, a corona charger has been used as a charging processing means for an image bearing member such as an electrophotographic photosensitive member or an electrostatic recording dielectric. It was

In recent years, because of advantages such as low ozone and low electric power, a contact charging device, that is, a charging member to which a voltage is applied as described above is brought into contact with the charged member to charge the charged member. System devices have been put to practical use.

A method of performing contact injection charging by applying a voltage to a contact conductive member such as a charging roller, a charging brush or a charging magnetic brush, and injecting a charge into a trap level on the surface of an object to be charged has been described in Japan Hardcopy 1992. Proceedings P
As described in "Contact Charging Characteristics Using Conductive Roller" in 287, these methods use a low resistance charging member that applies a voltage to a dark insulating photoconductor as a member to be charged. This is a method of charging, and it has been a condition that the resistance value of the charging member is sufficiently low and that the material (conducting filler or the like) that makes the charging member conductive is sufficiently exposed on the surface.

In particular, when contact injection charging is performed, it is desirable that the charging member and the member to be charged contact each other frequently. Therefore, the shape of the charging member is preferably a brush shape rather than a roller shape.

In the brush-shaped charging member, generally, the higher the brush density is, the better the charging uniformity is. However, since the brush density is high, it is difficult to carry out minute charging by contacting one brush with the other. In some cases, the charging became uneven.

[0008]

OBJECTS OF THE INVENTION It is an object of the present invention to reduce electrical contact between charging brushes.

Another object of the present invention is to perform uniform charging with a charging brush.

[0010]

According to the present invention, there is provided a charging member which has a base and a brush member, and which is charged with a voltage to charge an object to be charged, wherein the brush member is electrically connected to the base. A charging member, comprising: a core member; and a coating layer that is coated on the conductive core member and has a volume resistivity higher than that of the conductive core member, or charging for charging an image carrier with the charging member. It is to provide a device.

[0011]

【Example】

(First Embodiment) (FIG. 1) (1) Example of Image Forming Apparatus FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus. The image forming apparatus of this example is a laser beam printer using a transfer type electrophotographic process.

Reference numeral 1 is a rotary drum type electrophotographic photosensitive member as an image bearing member. This embodiment is an OPC photosensitive member having a diameter of 30 mm, and is rotationally driven in the clockwise direction indicated by an arrow at a process speed (peripheral speed) of 100 mm / sec.

Reference numeral 2 denotes a rotating brush roller (charging brush) as a contact charging member which is brought into contact with the photosensitive member 1. A charging bias applying power source S is applied to an electrode 2a of the rotating charging brush 2.
A DC charging bias of 1 to -1200V is applied, and the outer peripheral surface of the photoconductor 1 is uniformly charged to approximately -680V by discharge.

Intensity modulation corresponding to a time series electric digital pixel signal of target image information output from a laser beam scanner (not shown) including a laser diode, a polygon mirror, etc., on the charged surface of the rotating photosensitive member 1. Scanning exposure L is performed by the generated laser beam, and an electrostatic latent image corresponding to target image information is formed on the peripheral surface of the rotating photoconductor 1.

The electrostatic latent image is reversely developed as a toner image by the reversal developing device 3 using a magnetic one-component insulating negative toner. Reference numeral 3a is a non-magnetic developing sleeve having a diameter of 16 mm and containing a magnet. The developing sleeve is coated with the above-mentioned negative toner so that the distance from the surface of the photoconductor 1 is 300.
While being fixed at μm, the developing bias voltage is applied from the developing bias power source S2 to the sleeve 3a by rotating the photosensitive member 1 at a constant speed. As the voltage, a DC voltage of -500 V and a rectangular AC voltage having a frequency of 1800 Hz and a peak-to-peak voltage of 1600 V are superimposed, and jumping development is performed between the sleeve 3 a and the photoconductor 1.

On the other hand, a transfer material P serving as a recording material is fed from a paper feeding section (not shown), and the rotary photosensitive member 1 is brought into contact with the rotary photosensitive member 1 with a predetermined pressing force. Is introduced into the pressure contact nip portion (transfer portion) T with the transfer roller 4 at a predetermined timing. A predetermined transfer bias voltage is applied to the transfer roller 4 from the transfer bias applying power source S3.

In this embodiment, a transfer roller 4 having a roller resistance value of 5 × 10 ⁸ Ω was used, and a DC voltage of +2000 V was applied to transfer.

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

The transfer material P to which the toner image has been transferred is separated from the surface of the photoconductor 1 and is introduced into a fixing device 5 such as a heat fixing system to be fixed with the toner image to form an image formed product (print, copy). Is discharged outside the device.

The surface of the photosensitive member after the transfer of the toner image onto the transfer material P is cleaned by the cleaning device 6 to remove adhered contaminants such as residual toner, and is repeatedly used for image formation.

In the image forming apparatus of this embodiment, four process equipments, that is, the photosensitive member 1, the contact charging member 2, the developing device 3 and the cleaning device 6 are included in the cartridge 20 so that they are integrated with the main body of the image forming apparatus. It is a cartridge type device that can be detached and replaced. The process cartridge may include at least the photoconductor 1 and the charging member 2.

(2) Photosensitive member 1 The electrophotographic photosensitive member 1 as the member to be charged in this embodiment is a negatively charged OPC photosensitive member, and the following first to fourth parts are formed on an aluminum drum base having a diameter of 30 mm. 4 functional layers are sequentially provided from the bottom.

The first layer is an undercoat layer and is provided to smooth defects such as an aluminum drum substrate (hereinafter referred to as an aluminum substrate) and to prevent moire due to reflection of laser exposure. The conductive layer has a thickness of about 20 μm.

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

The third layer is a charge generation layer, which is a layer having a thickness of about 0.3 μm in which a disazo pigment is dispersed in a resin, and positive and negative charge pairs are generated by laser exposure.

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

(3) Contact charging member 2 Charging brush 2 as a contact charging member in this embodiment.
As shown in FIG. 1 (b), the inner needle 2c as a core member is made of conductive nylon having a diameter of 78 to 80 microns and a volume resistivity of 10 ⁷ Ωcm or less. Is provided with a resistance coating 2d of 10 ¹⁰ Ωcm or more, and conductive fibers of a double structure having an outer diameter of about 80 microns and a length of 1 mm are formed on a conductive polycarbonate substrate 2b having a thickness of 1 mm and a volume resistance of 10 ⁴ Ωcm. A sheet obtained by electrostatically flocking is used as a roll brush having an outer diameter of 14 mm, which is wound, and has a density of about 50,000 filaments per square inch. The volume resistivity of the coating 2d is set to be larger than the volume resistivity of the inner needle 2c.

The substrate 2b is supported on the electrode 2a made of SUS or aluminum. Brush resistance is about 1
It is × 10 ⁷ Ω. (This resistance value is a metal diameter of 30
The values are converted from the value of current flowing when a voltage of 100 V is applied to a drum having a diameter of 3 mm with a nip width of 3 mm. By using this double-structure charging brush, it is possible to charge the photoconductor 1 by discharging by injecting charges into the trapping potential on the surface of the photoconductor. Also,
Since the charging brush has a double structure, electrical contact between the brushes can be practically eliminated, and uniform charging is possible. The inner needle 2c has a diameter of 5 to 80 μm and a volume resistivity of 10 ⁷ Ωcm or less, and the coating 2d has a thickness of 1
˜40 μm, the volume resistivity is 10 ¹⁰ Ωcm or more, and the substrate 2b desirably has a volume resistivity of 10 ⁴ to 10 ⁷ Ωcm.

In the present embodiment, a charging brush having about 50,000 filaments per square inch is used to obtain 300
dpi (pixel density of 300 dots per square inch)
The charging in step 1 can be almost practically satisfactory.

In the present embodiment, charging is performed by bringing the charging brush, to which the DC voltage of -1200V is applied to the electrode 2a as described above, into contact with the photosensitive member 1 and rotating it.

As described above, the charging is performed by injecting the charge from the charging brush 2 to the trapping potential on the surface of the photosensitive member 1. Therefore, it is more uniform when the charging brush 2 is in contact with the entire surface of the photosensitive member. Can be charged.

In the case of this embodiment, the existence of the discharge threshold value between the charging brush 2 and the photosensitive member 1 is recognized.

(Second Embodiment) This embodiment is shown in FIG.
As shown in (b), the inner needle 2c has a diameter of 5 to 20 μm and a volume resistivity of 10 ⁴ to 10 ^{7 as} compared with the first embodiment.
Ωcm, the outer layer 2d has a thickness of 1 to 10 μm and a volume resistivity of 10 ¹⁰ to 10 ¹⁶ Ωcm, and the resistance value of the substrate 2b on which the brush is brushed is 10 ⁴ to 10 ⁷ Ωcm. Is characterized by having on its surface a charge injection layer made of a material having a resistance value of 1 × 10 ¹⁰ to 1 × 10 ¹⁴ Ωcm. The base structure of the charging brush including the base 2b, the inner needle 2c, and the outer layer 2d is the same as that of the first embodiment.

In this embodiment, members having the same functions as in Embodiment 1 except for the surface layer of the photosensitive member are designated by the same reference numerals, and the same description is omitted for simplification.

(1) Example of Image Forming Apparatus An image forming apparatus similar to that in Example 1 was used, but in this example, the electrode 2a of the rotating brush 2'is supplied with a charging bias power source S1 from -700V. The DC charging bias is applied. At this time, the outer peripheral surface of the rotating photoconductor 1 is uniformly charged to approximately −680V. That is, the applied voltage to the brush 2'and the charging potential of the photoconductor 1 are almost the same.

(2) Photoreceptor 1 Electrophotographic photoreceptor 1 as a member to be charged in this embodiment
Is a negatively-charged OPC photosensitive member, in which the following first to fifth functional layers are provided in order from the bottom on an aluminum drum base having a diameter of 30 mm. The photosensitive layer 11 is
It is composed of the following four layers from the first layer to the fourth layer.

The first layer is an undercoat layer and is provided to smooth defects such as the aluminum drum substrate 10 (hereinafter referred to as aluminum substrate) and to prevent moire due to reflection of laser exposure. The conductive layer has a thickness of about 20 μm.

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

The third layer is a charge generation layer, which is a layer having a thickness of about 0.3 μm in which a disazo pigment is dispersed in a resin, and positive and negative charge pairs are generated by laser exposure.

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

The fifth layer is the charge injection layer 12, which is a feature of this embodiment, and is a coating layer made of a material in which SnO ₂ ultrafine particles 12a are dispersed in a photocurable acrylic resin as a binder. Specifically, a material in which 70 wt% of SnO ₂ particles having a particle diameter of about 0.03 μm obtained by doping acrylic resin with antimony, which is a light-transmitting conductive filler, to reduce resistance (conductivity) is dispersed in the resin. Coating layer.

In practice, as described above, the resistance value of the charge injection layer must be 1 × 10 ¹⁰ to 1 × 10 ¹⁴ Ωcm in order to satisfy the conditions of not causing sufficient chargeability and image deletion. Therefore, for this reason, it is preferable that the added amount of SnO ₂ be within the range of 2 to 100% by weight with respect to the binder.

The coating solution thus prepared is applied to a thickness of about 3 μm by a suitable coating method such as a dipping coating method, a spray coating method, a roll coat coating method and a beam coat coating method to form a charge injection layer. And

The binder of the charge injection layer may be the same as the binder of the charge transport layer, but in this case, the coating surface of the charge transport layer may be disturbed when the charge injection layer is coated. Therefore, it is necessary to particularly select the coating method.

As a result, the resistance of the surface of the photosensitive member was 1 × 10 ¹⁵ Ωcm in the case of the charge transport layer alone, compared with 1 × 10 ¹⁵ Ωcm.
It decreased to 10 ¹¹ Ωcm.

(3) Contact charging member 2'Charging brush 2'as a contact charging member in this embodiment.
Of the inner needle 2c has a diameter of 5 to 20 μm and a volume resistivity of 10
Made of conductive nylon of ⁴ to 10 ⁷ Ωcm and thickness of 1 to 10μ
m has a volume resistivity of 10 ¹⁰ to 10 ¹⁶ Ωcm or more and is provided with a resistance coating 2 d, and a conductive fiber having a double structure with an outer diameter of about 5 to 20 μm and a length of 1 mm has a thickness of 1 mm and a volume resistance value of 1
A roll brush having an outer diameter of 14 mm is wound around a sheet in which electrostatically flocked bases 2b made of a conductive polycarbonate of 0 ⁴ Ωcm are wound, and the density is about 50 to 60,000 filaments per square inch. . The base 2b
Are supported on the electrodes 2a.

The brush resistance value is 1 × 10 ⁷ Ω. (Converted from a current value flowing when a voltage of 100 V is applied to a drum made of metal and having a nip width of 3 mm and having a nip width of 3 mm) By using this double structure charging brush 2 ', Even if a defect such as a pinhole occurs above, it is possible to prevent an excessive leak current from flowing into this portion.

The volume resistivity of the substrate 2b is preferably 10 ⁴ Ωcm or more in order to prevent leakage, and is preferably 10 ⁷ Ωcm or less in order to improve charging efficiency.

Further, since the charging brush has a double structure, electrical contact between the brushes can be practically eliminated, and uniform charging is possible.

In this embodiment, a charging brush having about 50,000 to 60,000 filaments per square inch is used.
Not only 300 dpi (pixel density of 300 dots per 1 square inch), but also 600 dpi, a good image can be obtained.

(4) Principle of Charging In the present embodiment, the contact charging member 2'having a medium resistance is used to inject charges into the surface of the photoconductor as a member to be charged having a surface resistance of medium resistance. The embodiment does not inject charges into the trapping potential of the surface material of the photoconductor, but the principle is to charge the conductive particles in the charge injection layer with charges.

Specifically, as shown in the enlarged view of the charging brush portion of FIG. 2A and the equivalent circuit of FIG. 2B, the charge transport layer 11 of the photoconductor 1 is made of a dielectric and an aluminum base 10. This is based on the theory that the contact charging member 2 charges a minute capacitor having the conductive particles 12a in the charge injection layer 12 as both electrode plates.

At this time, the conductive particles 12a are electrically independent of each other and form a kind of minute float electrode. For this reason, the surface of the photoconductor seems to be charged and charged to a uniform potential on a macroscopic scale, but in reality, countless minute charged SnO ₂ particles 12a cover the surface of the photoconductor. Has become.

Therefore, each SnO ₂ particle 12a is electrically independent from each other even when imagewise exposure is performed by a laser, so that an electrostatic latent image can be held.

Therefore, in this embodiment, the trap level, which was present on the surface of the conventional photoconductor in a small amount, was used as SnO.
It is a substitute for ₂ particles.
The charge retention property is improved.

In order to perform good charge injection charging with a conventional photoreceptor, the charge value of the charging member 2 is 1 × 1 because charge injection must be efficiently carried out at a small number of trap points.
It is not less than 0 ³ Ω, and the resistance value of an ordinary surface material of a photoreceptor is about 1 × 10 ¹⁵ cm.

On the other hand, when the charge injection layer 12 is provided, the area where the charge can be held increases on the surface of the photoconductor, so that good charging can be performed even if the charging member 2'having a higher resistance value is used. It

Actually, the resistance value of the charge injection layer 12 is 1 × 1.
If it is in the range of 0 ¹⁰ to 1 × 10 ¹⁴ Ωcm, charging can be performed with good efficiency such that the surface potential of the photoconductor charged to the applied voltage is 90% or more even with a charging member of 1 × 10 ⁷ Ω. is there.

On the other hand, when a pinhole is generated on the surface of the photoconductor, leakage does not occur and the photoconductor 1 and the charging member 2 are not destroyed, or the entire charging member 2'causes a voltage drop due to a leak current and contacts the charging member. It has been experimentally confirmed that the charging member 2'has a resistance value of 1 × 10 ⁴ Ω or more so as not to cause defective charging of the entire part.

Actual examples are shown in Table 1. From this table, according to the present invention, the contact charging member 2'having a resistance value of 1 × 10 ⁴ to 1 × 10 ⁷ Ω is 1 × 10 ¹⁰ to 1 ×. It can be seen that by charging the photoconductor 1 having the charge injection layer 12 having a resistance value of 10 ¹⁴ Ωcm, it is possible to configure a charging system that satisfies good charge injection property and anti-pinhole property.

[0061]

[Table 1]

The term "leak" means that when a pinhole is formed on the photosensitive member, it is charged but leaks.

In this embodiment, as described above, -70
Charging is performed by bringing the charging brush 2 to which a DC voltage of 0 V is applied into contact with the photoconductor 1 and rotating the same.

As described above, the charging is performed by the charging brush 2 '.
Is performed by injecting charges into the SnO ₂ particles 12a on the surface of the photoconductor 1, the charging brush 2 must be in contact with the entire surface of the photoconductor. Therefore, FIG. 3 shows the result of measurement of the charging efficiency when the rotation speed of the charging brush 2 is changed with the contact nip width N of the charging brush 2 ′ set to 2 mm.

Here, the surface potential of the photoconductor is once lowered to OV, and the potential is represented by a potential that can be charged by the photoconductor 1 passing once through the nip N of the charging brush 2 '.

Here, the peripheral speed of the photosensitive member 1 is defined as V _K , the peripheral speed of the charging brush 2'is defined as V _B , and the nip width formed by the charging brush 2'and the photosensitive member 1 is defined as N. Assuming that the ratio is (V _K −V _B ) / V _K , the charging efficiency depends on the peripheral speed ratio, and V that rotates the charging brush 2 relative to the photoconductor 1 in the counter direction at a constant speed.
_{When B} = -V _K , that is, by setting the peripheral speed ratio to 2 or more,
It has been found that it is possible to provide sufficient potential convergence. Therefore, we decided to carry out the experiment under these conditions.

This is to secure the charging time by giving the peripheral speed ratio, and to increase the chances of contact between the photoconductor 1 and the charging brush 2, and if the charging nip width N is further increased. It is possible to perform good charging even if the peripheral speed ratio is reduced.

Therefore, the value N · (V _B −V _K ) / V _K obtained by multiplying the charging nip width N by the peripheral speed ratio has a close relation with the charging efficiency, and if this value is 4 [mm] or more. It was found that good charging efficiency such that the charging potential was 90% or more with respect to the applied voltage was obtained.

When an experiment was actually carried out with the charging nip width N being 2 mm and 3 mm, when the peripheral speed ratio was 2 or more when the charging nip width N = 2 mm, the charging was not possible with 90% efficiency. When the nip width N = 3 mm, similar charging can be performed even when the peripheral speed ratio is 1.3.

As can be seen from FIG. 3, when the peripheral speed ratio is 0, charging is most difficult. This is because the chance of contact between the photoconductor 1 and the contact charging member 2 is the smallest when the peripheral speed ratio is 0, and in order to perform charge injection charging efficiently, the contact charging member 2 ′ and the photoconductor 1 must be contacted. It is necessary to have a peripheral speed ratio.

In such a state, as shown in FIG. 4, the applied voltage to the charging brush 2'and the surface potential of the photosensitive member 1 change substantially linearly, and the discharge threshold value as in the case of using the conventional charging roller is set. Is not recognized, indicating that charge injection is being performed.

On the other hand, it can be seen from FIG. 4 that charge injection is less likely to occur when the conventional ordinary photosensitive drum is used, and there is a discharge threshold value. Further, from FIG. 3, the potential convergence is achieved in the conventional photosensitive drum. It is obvious that it is inferior in sex.

In this way, the charging brush 2 is -70
When a voltage of 0V is applied, the photoconductor is charged to approximately -680V.

(5) Transfer Means 4 In the transfer means using a corona charger that has been generally used in the past, the transfer plus memory to the photosensitive member when the reversal phenomenon was performed was relatively small, but recently it is low. When the contact transfer means 4 such as a transfer roller which has been put into practical use from the viewpoint of ozone is used, the contact transfer member 4 is directly discharged to the photoconductor 1, so that positive memory is likely to occur.

Further, when this is combined with the conventional contact charging member, the contact charging device has a smaller charging area than the conventional corona charging device, so that partial charging failure due to plus memory is unavoidable and the transfer roller of the transfer roller cannot be avoided. There has been a need for optimizing the resistance value and performing complicated control such as transfer bias.

The mechanism of generation of plus memory is considered as follows. First, the positive charge charged by the transfer charger moves inside the photoconductor and stays inside the charge transport layer without being absorbed by the conductive substrate of the photoconductor.
Even if the surface of the photoconductor is uniformly negatively charged during the next primary charging, the positive charges staying inside the photoconductor move to the surface again and cancel the negative charges on the surface. That is, a charging failure may occur.

However, when the photoconductor 1 having the charge injection layer 12 on the surface is used, the plus memory is less likely to occur. This is because the positive memory received from the transfer charger does not move to the inside of the photoconductor and is retained in the charge injection layer, so that the positive charge is quickly canceled during the primary charging, and uniform negative charging is possible. Is.

This effect is remarkable when the charging member 2'has a high resistance value and a small charging area and thus has a low charging ability. When the transfer roller 4 is used, the effect of providing the charge injection layer is particularly great. .

Therefore, in the case of an electrophotographic apparatus provided with a contact transfer member such as the transfer roller 4, the resistance value of the charging member 2'is 1 × 10 ^{4 in} the sense of preventing plus memory as described above. desirably it has accommodated a range of ~1 × 10 ⁷ Ω, 1 × of 10 ⁷ Omega more resistance charging member 2
In the case of the provision of, the partial charging failure due to the plus memory becomes remarkable.

When an image was output by the printer of this embodiment having the above-mentioned structure, a good image could be output under any environment. At this time, the voltage applied to the charging member 2 is only −700 V corresponding to the charging potential, and it is no longer necessary to apply an extra voltage for exciting discharge as in the conventional contact charging device.

Further, from this fact, it becomes possible to completely eliminate the generation of ozone and the deterioration of the surface of the photoconductor, which have been conventionally caused by discharge.

(Third Embodiment) This embodiment is the same as the first embodiment.
It is characterized in that the brushes are fixed between the charging brushes of Example 2 with a material having a volume resistivity of 10 ¹⁰ Ωcm or more.

The charging member of this embodiment is shown in FIG.

In FIG. 5, a core metal 2a having a diameter of 6 mm, a base material 2b, an inner needle 2c and an outer layer 2 which are the same as those in FIG.
A charging brush having d is formed, and in the present embodiment, urethane rubber is adjusted to the above resistance value as the fixing member 2e between the brushes, and is formed into a substantially roller shape.

Further, the surface is polished so that the brush tip of the double structure and the roller surface are flush with each other.

Using the same image forming apparatus and photoconductor as in Example 1, the chargeability was confirmed, and the same results as in Example 1 were obtained.

In this example, it was confirmed that the non-uniform charging due to the collapse of the brushes is reduced because the brushes are fixed.

As a modification of this embodiment, the second embodiment will be described.
5 is formed by using a fixing member 2e made of a urethane material having a low efficiency of 10 ¹⁰ Ωcm or more, and a charging member having the same structure as that in Example 2 is formed. Was evaluated.

As for the embodiment, more uniform charging than that of the embodiment 2 was performed.

Although urethane is used as the material for fixing the brushes having the double structure, the same effect can be obtained by using, for example, EPDM foam.

(Fourth Embodiment) In this embodiment, the charging member according to the third embodiment is characterized in that the tip of the brush having the double structure is projected more than the diameter of the inner needle 2c more than other portions. Is.

FIG. 6 is a schematic view of the charging member used in this example.
Shown in

The present embodiment is characterized in that the fixing member 2e is fixed between the charging brushes of the first embodiment with a material having a volume resistivity of 10 ¹⁰ Ωcm or more.

In FIG. 6, a charging brush is formed on a cored bar 2a having a diameter of 6 mm in the same manner as in the first embodiment. In this embodiment, urethane rubber is adjusted to the above resistance value as the fixing member 2e and formed into a substantially roller shape. It was formed.

The double-structured brush used in this embodiment is
The inner needle 2c has a thickness of 20 μm and the outer layer 2d has a thickness of 10 μm. Brush tip is 20 to 1
It is projected about 00 microns.

When the same evaluation as in Example 1 was performed in this example, a better charging property than in Example 3 could be obtained.

Even when the same double-structured brush as in Example 2 was used, better results than in Example 3 were obtained.

(Fifth Embodiment) This embodiment corresponds to the first embodiment,
A plate-shaped charging brush of Example 2 is used as a charging member.

A schematic view of the charging member of this embodiment is shown in FIG.

In FIG. 7, the plate-shaped charging member 15 of the first embodiment has a metal support member (electrode) 150 and a brush 152 having a double structure electrostatically implanted on a base of conductive polycarbonate 151. Is. The brush 152 is
It consists of the inner needle 2c and the outer layer 2d of FIG. 1 (b).

In this embodiment, the charging member 15 is supported so as to be in contact with the photoconductor 1 in the forward direction and have a nip width of 3 mm with the photoconductor. The length L of the charging member in the rotating direction is 10 mm.

When an image was formed using the same image forming apparatus as in Example 1, almost the same results as in Example 1 were obtained.

From the viewpoint of manufacturing, the charging member on the plate of this embodiment can be manufactured by performing electrostatic flocking, cutting, and adhering it to the supporting member 150, so that there is an advantage that it can be manufactured at low cost.

(Sixth Embodiment) This embodiment is characterized by using a developer having a shape factor SF-1 of 150 or less.

The charging member and the image forming apparatus used are the same as in the first embodiment.

The shape factor SF-1 in this embodiment is
It is shown below and in FIG.

That is, as shown in FIG. 8, it is a numerical value showing the ratio of the roundness of the shape of the spherical substance, and the square of the maximum length MXLNG of the elliptical figure formed by projecting the spherical substance on the two-dimensional plane is plotted as a figure. It is represented by a value when divided by the area AREA and multiplied by 100π / 4. That is, the following expression of the shape factor SF1, SF1 = {(MXLNG) ² / AREA} × (100π
/ 4).

In this embodiment, the developer used was a one-component magnetic toner, and the toner produced by the pulverization method was further spheronized to obtain the above-mentioned shape factor.
The toner particle diameter is 6 to 7 microns in volume average diameter.

Further, 1.2% of silica was added to the toner as an external additive after the spheroidizing treatment.

As a result of using this developer, the adhesion of toner to the charging member was reduced and the charging performance in durability was improved. The results are shown in Table 2. 1,000, 20,000, 40
000 sheets is the number of A4 size plain paper transfer materials on which images are formed.

[0111]

[Table 2]

Here, ◯ indicates a state where the charging property is uniform, and Δ indicates a range where the charging property is not uniform but there is no problem in practical use. Δ × is an item that requires practical improvement.

(Seventh Embodiment) This embodiment has a shape factor SF-1 of 110 or less in the sixth embodiment, and is a toner produced by a polymerization method.

The toner used in this example is a non-magnetic one-component developer containing no magnetic substance.

The average particle diameter is about 6 μm in volume average diameter.

The charging member and the image forming apparatus used in this embodiment are the same as those in the sixth embodiment.

The results of this example will be described in Table 3 in comparison with the comparative example using the pulverized toner. 2000 sheets,
40,000 sheets and 80,000 sheets are the number of A4 size plain paper transfer materials on which images are formed.

[0118]

[Table 3]

As shown in Table 3, the shape factor SF-1 is 1
When it is 10 or less, the durability performance is further improved.

Here, in Table 3, ◯, Δ, and Δ × are the same as those in the above-described embodiment, and x indicates that improvement is necessary.

In this embodiment, a non-magnetic developer is used as the toner used, but the same applies when a magnetic developer is used.

[0122]

According to the present invention, since the brush member is provided with the conductive core member and the clothing layer, electrical contact between the brushes is reduced, and uniform charging can be performed.

[Brief description of drawings]

FIG. 1 is an explanatory view of a first embodiment of a charging member of the present invention.

FIG. 2 is an explanatory diagram of a second embodiment of the present invention.

FIG. 3 is a graph showing the relationship between the peripheral speed ratio and the drum potential.

FIG. 4 is a graph showing the relationship between applied DC voltage and drum potential.

FIG. 5 is an explanatory diagram of a third embodiment of the present invention.

FIG. 6 is an explanatory diagram of a fourth embodiment of the present invention.

FIG. 7 is an explanatory diagram of a fifth embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a shape factor SF-1 of a developer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 2, 2'Charging member 2a Electrode 2b Base 2c Inner needle 2d Coating 10 Drum base 11 Photosensitive layer 12 Charge injection layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takushi Shibuya 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Satoshi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Yasuo Yoda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (18)

[Claims] 1. A charging member, comprising a base and a brush member, for applying a voltage to charge an object to be charged, wherein the brush member is a conductive core member electrically connected to the base. And a coating layer that covers the conductive core member and has a volume resistivity higher than that of the conductive core member. 2. The conductive core member has a diameter of 5 to 80 μm.
m, the volume resistivity is 10 ⁷ Ωcm or less, the coating layer has a thickness of 1 to 40 μm, the volume resistivity is 10 ¹⁰ Ωcm or more, and the substrate has a volume resistivity of 10 ⁴ to 10 ⁷ Ωc.
The charging member according to claim 1, wherein the charging member is m. 3. The conductive core member has a diameter of 5 to 20 μm.
m, the volume resistivity is 10 ⁴ to 10 7 Ωcm, the coating layer has a thickness of 1 to 10 μm, and the volume resistivity is 10 ¹⁰ to ¹⁰ 10.
The charging member according to claim 2, wherein the charging member has a resistance of ¹⁶ Ωcm. 4. The charging member has a total resistance value of 1 × 10 ⁴
It is about 1 × 10 ⁷ Ω.
Charging member. 5. The charging member according to claim 1, wherein the charging member includes a fixing member having a resistance of 10 ¹⁰ Ωcm or more for fixing between the brush members. 6. The charging member according to claim 1, wherein a tip end of the brush member projects more than a diameter of the conductive core member more than the other portion of the charging member. 7. A charging device comprising: a base member; and a brush member in contact with the image carrier, the charging device comprising a charging member for applying a voltage to charge the image carrier, wherein the brush member is electrically connected to the base member. 1. A charging device comprising: a conductive core member that is electrically connected to the conductive core member; and a coating layer that is coated on the conductive core member and has a volume resistivity higher than that of the conductive core member. 8. The conductive core member has a diameter of 5 to 80 μm.
m, the volume resistivity is 10 ⁷ Ωcm or less, the coating layer has a thickness of 1 to 40 μm, the volume resistivity is 10 ¹⁰ Ωcm or more, and the substrate has a volume resistivity of 10 ⁴ to 10 ⁷
The charging device according to claim 7, wherein the charging device is Ωcm. 9. The conductive core member has a diameter of 5 to 20 μm.
m, the volume resistivity is 10 ⁴ to 10 7 Ωcm, the coating layer has a thickness of 1 to 10 μm, and the volume resistivity is 10 ¹⁰ to ¹⁰ 10.
The charging device according to claim 8, wherein the charging device has a resistance of ¹⁶ Ωcm. 10. The charging member has a total resistance value of 1 × 10.
The charging device according to claim 7, wherein the charging device has a resistance of ⁴ to 1 × 10 ⁷ Ω. 11. The image carrier has 1 × 10 5 on its surface.
The charging device according to claim 7, further comprising a charge injection layer having a volume resistivity of ¹⁰ to 1 × 10 ¹⁴ Ωcm. 12. The charging device according to claim 7, wherein the voltage is a DC voltage. 13. The charging device according to claim 7, wherein the charging member is provided with a fixing member having a resistance of 10 ¹⁰ Ωcm or more for fixing between the brush members. 14. The charging device according to claim 7, wherein a tip end of the brush member projects more than a diameter of the conductive core member more than the other portion of the charging member. 15. The charging device according to claim 7, wherein the charging member is rotatable. 16. The charging device according to claim 7, wherein the charging member has a plate shape. 17. The charging device according to claim 7, wherein the image carrier is developed with a developer having a shape factor SF-1 of 150 or less. 18. The shape factor SF-1 of the developer is 11
18. The charging device according to claim 17, which is 0 or less.