JPH05216326A - Contact type electrostatic charge device and production of electrostatic charge member provided therein - Google Patents

Abstract

PURPOSE:To prevent defective electrostatic charge from occurring, to prevent the efficiency of the electrostatic charge from being deteriorated and to achieve a stable electrostatic charge function without receiving the effect of environmental conditions by using a contact layer obtained by dispersing and mixing a low resistance part and a high resistance part as the contact layer between an electrostatic charge member and a body to be electrostatically charged. CONSTITUTION:As for the contact layer 7 of the electrostatic charge member such as an electrostatic charge roller 5, both of the low resistance part 10 and the high resistance part 11 are exposed on the front surface of the roller 5 and brought into contact with an electrical conductive substrate 6. Besides, the low resistance part 10 is electrically connected to the substrate 6. Then, it is preferable that the volume resistivity of the resistance part 10 is set to be within the range of 10<5>-10<7>OMEGA.cm and the volume resistivity of the resistance part 11 is set to be >=10<10>OMEGA.cm. The efficiency of the electrostatic charge and the stability of an environment with respect to a photosensitive body 1 are enhanced by the resistance part 10 and a current is prevented from being concentrated at the defective part of the body 1 by the resistance part 11. Thus, the roller 5 which does not cause both problems of the occurrence of the defective electrostatic charge and the deterioration of the electrostatic charge and which has small environmental dependability can be constituted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact charging device and a method of manufacturing a charging member included in the device.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a facsimile machine, a printer, or the like, which forms an electrostatic latent image on the surface of a latent image carrier, the latent image carrier is formed prior to the formation of the electrostatic latent image. The body surface is uniformly charged, and a charge of a predetermined polarity is placed on the surface.

A contact type charging device is known as such a charging device, and such a charging device is provided with a charging member for contacting a charged body such as a latent image carrier. The charging member is configured as a roller-shaped charging roller, for example.

The outermost layer portion of this type of charging member is desired to have a volume resistivity of 10 ^{8 to} 10 ¹⁰ Ω · cm. One of the reasons for this is that the volume resistivity is 1
If the surface resistance of the latent image carrier, which is the member to be charged, is 0 ⁷ Ω · cm or less, there is a defect such as a pinhole,
This is because a current flows intensively in this portion, and a charging failure due to a voltage drop easily occurs. When such a charging failure occurs, white spots, black blurring, or the like on the image may occur.

Another reason is that if the outermost layer portion has a volume resistivity of 10 ¹¹ Ω · cm or more, the surface potential of the charging member becomes lower with respect to the applied voltage, and the charging efficiency becomes higher. Because it will decrease. When such charging efficiency is lowered, a high-capacity high-voltage power source is inevitably needed.

For these reasons, it is desirable that the outer layer portion of the charging member has a volume resistivity of 10 ^{8 to} 10 ¹⁰ Ω · cm. On the other hand, in such a range, When ambient environmental conditions, especially humidity conditions change,
The volume resistivity is likely to change, and the intended function cannot be performed. Even if the environmental conditions change, it is difficult to find a material whose volume resistivity does not easily change and which is excellent in mechanical properties such as flexibility and abrasion resistance.

From such a point of view, the appearance of a contact charging device that does not cause problems such as a charging failure or a decrease in charging efficiency, and is not easily influenced by environmental conditions, has hitherto appeared. Was desired. As a charging device of this type, there has been already proposed a charging device having a two-layer structure charging member having different volume specific resistivities, as disclosed in JP-A-64-73364.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is that it does not cause problems such as defective charging or reduced charging efficiency, and that it is dependent on environmental conditions. It is another object of the present invention to provide a contact charging device capable of performing a stable charging function and a method of manufacturing a charging member in the device.

[0009]

In order to achieve the above-mentioned object, the present invention comprises a charging member for contacting a charged body and charging the surface of the charged body, the charging member applying a voltage. And a contact layer formed on the outer surface thereof for contacting the body to be charged, the contact layer of which is a contact layer in which a low resistance portion and a high resistance portion are dispersed and mixed. It proposes a device.

The volume resistivity of the low resistance portion is 10 ⁵
It is effective to set the volume resistivity of the high resistance portion to 10 ¹⁰ Ω · cm or more in the range of 10 to 10 ⁷ Ω · cm.

Further, in the production of the above-mentioned charging member, after the fiber having the high resistance portion and the low resistance portion is wound around the outer surface of the substrate to be coated, the volume resistivity of the low resistance portion is 10 or less.
It is effective to melt the fibers with a melting time that is in the range of ^{5 to} 10 ⁷ Ω · cm.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 schematically shows a contact charging device according to an embodiment of the present invention and a photoconductor whose surface is charged by the contact charging device.

Reference numeral 1 denotes a belt-shaped photosensitive member which is an example of a member to be charged, which is obtained by coating an OPC (organic photoconductor) on a substrate made of, for example, nickel. .. The photoconductor 1 is stretched between the three support rollers 2, 3 and 4 and is rotationally driven in the direction of arrow a.

Reference numeral 5 indicates a charging member, which in the present example is constituted by a roller-shaped member. Hereinafter, this is referred to as a "charging roller". The charging roller 5 comes into contact with the photoconductor 1 as shown in the drawing, and is rotationally driven in the direction of arrow b so that this contact portion moves in the same direction as the movement direction of the photoconductor surface.

The photosensitive member 1 and the charging member 5 shown in FIG. 1 together with other various elements constitute an image forming apparatus such as an electronic copying machine or a laser printer, and an electrostatic latent image is formed on the photosensitive member 1. Prior to the formation, the photoconductor 1 is uniformly charged by the charging member 5.

The charging roller 5 has a roller-shaped substrate 6 and a contact layer 7 formed on the outer surface of the roller-shaped substrate 6 and contacting the photoreceptor 1. The base 6 is a conductive base made of, for example, a good metal conductor such as aluminum, and the conductive base 6 is connected to a high-voltage power supply 8. The high-voltage power supply 8 polarizes the conductive base 6 to be charged. Is applied.

The contact charging device 100 of this embodiment is equipped with a charging roller 5 for uniformly charging the surface of the photoconductor 1 and a high voltage power source 8. The charging roller 5 has a diameter of, for example, about 16 mm, and when the polarity to be charged is negative by the high voltage power source 8, a voltage of, for example, about -1.5 KV is applied. Is applied. The photosensitive member 1 is, for example, 38 mm / in the direction of the arrow a.
It rotates at a linear velocity of about sec, and the charging roller 5 also rotates at the same linear velocity when coming into contact with the photoconductor 1 with a predetermined nip width.

Here, the feature of this embodiment is that the contact layer 7 of the charging member such as the charging roller 5 is a contact layer in which low resistance portions and high resistance portions are dispersed and mixed.

For example, as clearly shown in FIG. 2 and schematically shown in FIG. 1, the ground 10 of the contact layer 7 is an epoxy resin portion in which a conductive additive such as carbon is dispersed and mixed, and the ground The nylon particles 11 are uniformly dispersed and mixed. The part of the ground 10 is the low resistance part, and the other nylon particle part 11 is the high resistance part. In this way, one of the low resistance portion and the high resistance portion can be used as the ground, and the other can be uniformly dispersed and mixed in the ground.

Hereinafter, a portion indicated by reference numeral 10 is a "low resistance portion".
The portion indicated by the reference numeral 11 will be referred to as a “high resistance portion”. However, both the low resistance portion 10 and the high resistance portion 11 are exposed on the surface of the charging roller 5 and the conductive substrate 6 is exposed. They are in contact with each other, and the low resistance portion 10 is electrically connected to the base 6.

Here, it is desirable that the volume resistivity of the low resistance portion 10 is in the range of 10 ^{5 to} 10 ⁷ Ω · cm, and the volume resistivity of the high resistance portion 11 is 10 ¹⁰ Ω · cm or more.
With such a low resistance portion 10, high charging efficiency for the photoconductor 1 and environmental stability are enhanced, and the high resistance portion 1
1 can prevent the current from concentrating on the defective portion of the photoconductor 1 and cause neither the problem of defective charging nor the deterioration of the charging rate, and can configure the charging roller 5 having less environmental dependency.

The details of such an operation and the relationship between the volume resistivity of each of the low resistance portion and the high resistance portion will be clarified below through more specific examples and comparative examples.

The inventor of the present invention measured the volume resistivity of each of the low resistance portion and the high resistance portion, and the low resistance portion and the high resistance portion of the examples described later by the following method.

A square aluminum flat plate having a length of 80 mm and a width of 80 mm is prepared, and various materials forming a low resistance portion and a high resistance portion are applied or heat-fused on the flat plate to form 100
A film with a thickness of about μm is formed, and a flat plate with such a film is set in a Yokogawa Hewlett Packard 16008A resistance measuring cell. If the volume resistivity is 10 ⁸ Ω · cm or more, it is manufactured by the same company. The volume resistivity of each material was measured using a 4329A high resistance meter. Also, the volume resistivity is 10
^{For 8} Ω · cm or less, 4262A Digital L manufactured by the same company
The volume resistivity of each material was measured using a CR meter.

Further, the surface potential of the photosensitive member 1 was measured by the following method in order to evaluate the charging efficiency and charging failure of each example. As shown in FIG. 1, a surface electrometer 12 is prepared, this probe (probe) 13 is moved in the axial direction (arrow direction) of the photoconductor 1, and the photoconductor 1 is moved at a free position in this direction. The surface potential was measured. A Trek Model 344 was used as the surface electrometer.

Although a defect such as a pinhole may occur in this type of photoconductor 1, reference numeral 15 is used to check the state of current concentration near this part, that is, to evaluate the charging failure. Intentionally attach a pinhole as shown,
The surface potential of the area (charge-defective portion) 16 near the pinhole portion 15 was measured. The size of the pinhole is 0.
It was set to 5 mm. Further, in order to evaluate the charging efficiency, the surface potential of the region 18 sufficiently separated from the pinhole portion 15 was measured. The measurement environment conditions were as follows. Temperature 10 ° C, relative humidity 20% (low temperature, low humidity) Temperature 30 ° C, relative humidity 80% (high temperature, high humidity) Below, low temperature, low humidity is “LL”, high temperature, high humidity is “H”
H ".

Next, each embodiment will be described.

Example 1 A charging roller having a contact layer 7 as shown in FIG. 2 was used. First, a coating layer made of epoxy resin (carbon is dispersed) on a flat plate
Was measured and the volume resistivity was measured.
Each sample having a volume resistivity such as

[0030]

[Table 1]

Nylon particles 11 (average particle size 30 μm, volume resistivity 8.2 × 10 ¹⁰ Ω · cm (HH), 2.7 × 10 ¹⁰ Ω · cm) were added to the above four kinds of epoxy paints.
(LL)) in a volume ratio of 60%, the mixture is diluted with toluene, and the diluted product is sprayed onto an aluminum core metal (conductive substrate) at 200 μm by spraying.
After being applied at a thickness of m and cured by heating at 150 ° C. for 20 minutes, the surface roughness Ra is 0.8 to 1.2 μm,
The cured surface was polished.

Comparative Example 1 At the same time, samples of charging rollers to which nylon particles 11 were not added were prepared as follows, and these were compared with the above. Sample A ': No nylon particles added to Sample A Sample B': No nylon particles added to Sample B Sample C ': No nylon particles added to Sample C Sample D': Nylon particles added to Sample D What not

Example 2 A charging roller having a contact layer 17 as shown in FIG. 3 was used.

In FIG. 4, reference numeral 22 indicates a conductive portion (low resistance portion) 21 partially made of carbon, for example.
Is a nylon fiber. As described above, the temperature around the Teijin nylon fiber (trade name “cell cut”) having the high resistance portion and the low resistance portion is heated at about 100 ° C., and the heated fiber is contracted, so that the conductive substrate 6 (see FIG. ) On the outer surface of
The conductive base is spirally wound and covered so as not to be exposed, and then the wound base is heated in a nitrogen gas atmosphere in a heating device to set the temperature of the conductive base (core metal) to 250.
While maintaining at 0 ° C., the fiber was melted by placing it in a heated state for 20 minutes to form a film-shaped contact layer 17. A filament winding device manufactured by Asahi Engineering Co., Ltd. was used for winding the fibers.

In FIG. 3, the reference numeral K indicates the boundary between the fibers 22, but this boundary disappears as the nylon fiber 22 melts, and the low resistance portion 21 is replaced by the nylon base (high resistance portion). ) 20, they are uniformly dispersed and mixed.

On the other hand, the following two types of comparative charging rollers were manufactured. Comparative Example 2-1 Film-forming time of Example 2 was set to 10 minutes Comparative Example 2-2 Film-forming time of Example 2 was set to 30 minutes

Example 3 A charging roller having a contact layer 27 as shown in FIG. 5 was used.

In FIG. 6, reference numeral 32 is a polyester fiber in which a conductive portion (low resistance portion) 31 made of, for example, carbon is dispersed. Kuraray polyester fibers having such a low resistance portion and a high resistance portion (trade name “Kuracarbo”) are formed around the conductive base 6 (FIG. 1) so that the conductive base 6 is not exposed. After braiding at 55 °, this is heated in an atmosphere of nitrogen gas in a heating device, and while maintaining the temperature of the conductive substrate (core metal) 6 at 300 ° C., it is kept in a heated state for 20 minutes to remove the fibers. After melting and cooling, the cooled and hardened surface was polished to have a surface roughness of 0.8 to 1.2 μm.

For knitting the fibers 32, a 48-stroke braiding machine manufactured by Kokubu Iron Works Co., Ltd. was used.

In FIG. 5, the reference numeral K indicates the boundary portion of the woven fibers 32, but the melting of the fiber eliminates this boundary portion, and the low resistance portion 31 is exposed by polishing or the like. In addition, the polyester base portion (high resistance portion) 30 is uniformly dispersed and mixed. In any case, in this example, as in the case shown in FIG. 3, the ground portion 30 is the high resistance portion.
On the other hand, in the example of FIG. 2, the ground portion 10 is a low resistance portion.

In contrast to the third embodiment, the following 2
A variety of types of comparative charging rollers were produced. Comparative Example 3-1 Film-forming time of Example 3 was set to 10 minutes Comparative Example 3-2 Film-forming time of Example 3 was set to 30 minutes

The charging roller shown in each of the examples and comparative examples described above was used to charge the photoconductor 1 in the manner shown in FIG. 1 and shown above, and the evaluation results are summarized in Table 2 below.
And Table 3.

[0043]

[Table 2]

[0044]

[Table 3]

In Tables 2 and 3, the non-defect portion surface potential is the potential at the region 18 on the photoconductor 1 in FIG. The surface potential around the defective portion is the potential at the region 16 on the photoconductor 1. Regarding the charging efficiency, 50% or more is a good range, a value smaller than 50% is a bad range, and a charging failure of 10% or less is a preferable range, and a larger value is a charging failure. This is markedly marked, and those in the unfavorable ranges are marked with X in Tables 2 and 3.

Comparing A to D of Example 1, defective charging occurs when the volume resistivity of the low resistance portion is 10 ⁴ Ω · cm or less, and charging efficiency is slightly higher when 10 ⁸ Ω · cm or more. It turns out to be low.

Further, in A'to D'of Comparative Example 1, 10 ⁸ Ω
・ If it is less than cm, poor charging will occur. It is considered that this is because the insulating nylon particles 11 (FIG. 2) of Example 1 have the effect of preventing current concentration at the interface with the photosensitive member, which is the member to be charged.

Comparing Examples 2 to Comparative Example 2-2,
It can be seen that charging failure occurs when the film formation time is 10 minutes, and the charging efficiency is reduced when the film formation time is 30 minutes. It can be considered that this is also due to the difference in the volume resistivity of the low resistance portion.

In the case where the film formation time was 10 minutes (Comparative Example 2-1), the film surface was observed by a scanning electron microscope, and carbon in the conductive part of the fiber was scarcely diffused by heat and had a low resistance. It has been confirmed that the interface between the high resistance part and the high temperature part is clear. Considering the volume ratio of the low resistance portion (about 1/7) from the resistance of the entire film (almost controlled by the low resistance portion),
When the volume resistivity of the low resistance part 21 is calculated, it becomes 3 × 10 ⁴ Ω · cm (HH) to 4 × 10 ⁴ Ω · cm (LL).

By the same calculation, in the case where the film formation time is 20 minutes (Example 2), the volume resistivity is 2 × 10 ⁶ Ω · cm.
(HH) to 4 × 10 ⁷ Ω · cm (LL), and in the case of 30 minutes (Comparative Example 2-2), the volume resistivity is 4 × 10.
^{It became 8} Ω · cm (HH) to 4 × 10 ¹⁰ Ω · cm (LL). In the observation of these films, the aforementioned interface is gradually becoming unclear.

The volume resistivity of ordinary nylon fiber containing no carbon is 2.1 × 10 ¹⁰ Ω as a result of the measurement.
-Cm (HH) -3.5 * 10 < ¹³ > (ohm) -cm (LL).

Comparing Examples to Comparative Examples 3-2, in the case where the film forming time is 10 minutes (Comparative Example 3-1), charging failure occurs and the film forming time is 20 minutes (Example 3). ), And those of 30 minutes (Comparative Example 3-2) did not cause charging failure and there was no difference in charging efficiency. This can also be attributed to the difference in the arrow tension and volume resistivity.

In the case of the film forming time of 10 minutes (Comparative Example 3-1), the observation of the film surface with a scanning electron microscope showed that the carbon in the conductive part of the fiber was hardly thermally diffused. Considering the volume ratio of the low resistance portion (about 1/6) from the resistance of the entire film (almost controlled by the low resistance portion), the low resistance portion 21 (FIG. 4)
The volume resistivity of is calculated as 8 × 10 ⁴ Ω · c
It becomes m (HH) to 9 × 10 ⁴ Ω · cm (LL).

Computed in the same manner, when the film formation time is 20 minutes (Example 3), 3 × 10 ⁶ Ω · cm (HH) to 4 ×
In the case of 10 ⁶ Ω · cm (LL) and the film formation time is 30 minutes (Comparative Example 3-2), 4 × 10 ⁶ Ω · cm (HH) to 8
The change was × 10 ⁶ Ω · cm (LL), and the change was small. Further, an experiment was conducted with a film forming time of 40 minutes, but a series of evaluations were not carried out because a film having many defects was generated due to the generation of bubbles which are considered to be caused by the pyrolysis gas. or,
The volume resistivity of a normal polyester fiber containing no carbon is measured to be 2.5 × 10 ¹² (HH) to
It was 8.3 × 10 ¹⁴ Ω · cm (LL).

From these results, any of the first and second embodiments was obtained.
Also in the cases of 2 and 3, a low resistance portion (volume resistivity of 10 ⁵ to 10 ⁷ Ω · cm) and a high resistance portion (volume resistivity of 10 ¹⁰ Ω · cm or more) are formed on the outer surface of the charging roller. It has been found that a contact charging device can be obtained which has good charging efficiency and is less likely to cause defective charging in the vicinity of a defective portion (pinhole) on the surface of the member to be charged when the particles are dispersed and mixed.

Also, as in sample D ', 10 ⁸ to 10 ¹⁰
A charging device using a homogeneous coating with a volume resistivity of Ω · cm was able to give a stable surface potential to the body to be charged. Furthermore, as in Examples 2 and 3, by controlling the melting time of the fiber having a conductive portion, Example 3
It was possible to easily obtain a low-cost charging member having a stable charging function, which does not necessarily require polishing performed with the above.

That is, the volume resistivity of the low resistance part is 1
It is sufficient to melt the fibers having the high resistance portion and the low resistance portion as described above with the melting time (film forming time) in the range of 0 ^{5 to} 10 ⁷ Ω · cm. In any case, when the heating time is increased, the conductive additive (filler) such as carbon in the fiber is thermally diffused, and the volume specific resistance is increased. The present invention has been made paying attention to such a point.

In the charging member of each of the above-described embodiments, the conductive base 6 is made of a rigid material such as aluminum which does not have elasticity. However, the conductive base 6 may be made of an elastic material. Alternatively, by forming a film-like contact layer having the above-mentioned characteristics on the charging roller, the charging roller is brought into contact with a body to be charged such as a drum-shaped photosensitive body which is a rigid body with a predetermined nip width. be able to. Further, the charging member may be a belt-shaped member or a blade-shaped member other than the roller-shaped member. In this case, when it is difficult to make the conductive substrate having elasticity to have a volume resistivity of 10 ⁶ Ω · cm or less, the charging efficiency is lowered, but the volume resistivity is 10 ^You may make it use the thing of 7-10 ⁹ Ω * cm. Thus, the substrate on which the contact layer is laminated does not necessarily have to be made of a good conductor of metal such as aluminum. Further, it is also possible to use a substrate in which an intermediate layer having a larger volume resistivity than this is provided on a good conductor such as metal.

As a material for forming the series of charging members, various insulating materials such as resin such as nylon, polyester, epoxy, polycarbonate, fluorine, silicone or ceramics or ceramics are applied to the high resistance portion. be able to. For the low resistance portion, a material obtained by dispersing a conductive additive such as carbon or metal oxide in these materials can be used.

The present invention can also be applied to a contact charging device for imparting a charging action to a charged body such as a photoconductor to eliminate the charge, and is also used in equipment such as an electrostatic chuck and an electrostatic actuator. It can also be used as a charging device.

Incidentally, Japanese Patent Application No. 3-3053 relating to the present applicant
No. 04 discloses an invention in which a conductive substrate is coated with conductive and dielectric fibers, and the coated product is heated and melted to obtain a developing roller having a conductive portion and a dielectric portion on the surface. However, this is different from the present invention.

[0062]

According to the constitution of the first aspect, it is possible to obtain a contact charging device which has a good charging efficiency, is less likely to cause defective charging, and is less susceptible to environmental conditions.

According to the second aspect of the present invention, since the charging member has a low resistance portion having a volume resistivity of 10 ⁵ to 10 ⁷ Ω · cm on the surface thereof, the charging efficiency is high. Moreover, it is possible to charge the charged body without being affected by environmental conditions, and since it has a high resistance part with a volume resistivity of 10 ¹⁰ Ω · cm or more, surface defects of the charged body can occur. It is possible to prevent current concentration and the like, and it is possible to prevent charging failure from occurring.

According to the manufacturing method of the third aspect, the charging member can be manufactured easily, easily and at low cost.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing a configuration of a charging device, a belt-shaped photosensitive member, and the like according to an embodiment of the present invention.

FIG. 2 is an enlarged view showing an outer surface of an example of a charging member included in the charging device according to the exemplary embodiment of the present invention.

FIG. 3 is an enlarged view showing an outer surface of another example of the charging member included in the charging device according to the exemplary embodiment of the present invention.

FIG. 4 is an enlarged perspective view showing a part of fibers wound around a conductive substrate of a charging member of another example.

FIG. 5 is an enlarged view showing an outer surface of a charging member of another example.

FIG. 6 is an enlarged perspective view showing a part of fibers wound around a conductive substrate of a charging member of another example.

[Explanation of symbols]

 1 Belt-Shaped Photosensitive Member as Charging Member 5 Charging Roller as Charging Member 6 Base 7 Contact Layer 10 Low Resistance Part 11 High Resistance Part 17 Contact Layer 20 High Resistance Part 21 Low Resistance Part 27 Contact Layer 30 High Resistance Part 31 Low Resistance part

Claims (3)

[Claims] 1. A charging member for contacting an object to be charged and charging the surface of the object to be charged, the charging member including a substrate to which a voltage is applied, and the object to be charged formed on the outer surface of the substrate. A contact charging device comprising: a contact layer in contact with, and a contact layer in which the low resistance portion and the high resistance portion are dispersed and mixed. 2. The contact according to claim 1, wherein the volume resistivity of the low resistance portion is in the range of 10 ^{5 to} 10 ⁷ Ω · cm, and the volume resistivity of the high resistance portion is 10 ¹⁰ Ω · cm or more. Charging device. 3. A charging member for contacting an object to be charged and charging the surface of the object to be charged, the charging member being a base body to which a voltage is applied, and the object to be charged formed on the outer surface thereof. In the method for producing the charging member of the contact charging device, wherein the contact layer is a contact layer in which a low resistance part and a high resistance part are dispersed and mixed. After winding and covering a fiber having a high resistance portion and a low resistance portion, the volume resistivity of the low resistance portion is 10 ^{5 to} 10 ⁷
A method for producing a charging member, characterized in that the fibers are melted for a melting time in the range of Ω · cm.