JPH08211695A - Charging member for image forming apparatus - Google Patents

Abstract

(57) [Abstract] [Purpose] A charging member that comes into contact with an image bearing member at low cost, avoids damage to the image bearing member, adhesion of foreign matter, etc., and enables stable and uniform charging over a long period of time. Provide a member. In an image forming apparatus having an image carrier and a charging member in contact with the image carrier, the crystallinity of a resistance layer of the charging member in contact with the image carrier is appropriately set, or the resistance layer is in contact with the image carrier. The fluorine compound is disposed on the side as a particulate or thin layer so as to be exposed.

Description

Detailed Description of the Invention

[0001]

[Object of the invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus utilizing an electrostatic transfer process such as an electrostatic copying machine and a printer, and more particularly to a charging member thereof.

[0002]

2. Description of the Related Art In the well-known image forming apparatus as described above, as means for uniformly charging the photosensitive layer on the surface of the image bearing member, it has been recently disclosed in, for example, JP-A-63-7380. As described above, there has been proposed a device in which an elastic roller-shaped charging member is contact driven by an image carrier.

This type of charging member has the advantages that the applied voltage to the bed is lower than that using a conventionally known corona discharger and that the amount of ozone generated is extremely small. If the contact pressure is too high, the toner will be easily fused on the image carrier, and if it is too low, the gap between the image carrier and the charging roller will be too large, or unevenness will result in uneven charging. Is likely to cause poor charging.

Further, regarding the charging roller itself,
This type of charging roller is formed by stacking an elastic layer, a resistance layer, and a protective layer (surface layer) on a cored bar in this order. The elastic layer and the resistance layer adjust the volume resistivity by dispersing a conductive pigment in rubber or the like. It is usual to provide rubber with good elasticity, and requires a plasticizer or activator to prevent deterioration,
Further, a dispersion aid may be used to disperse the conductive pigment.

On the other hand, the image carrier is made of polycarbonate,
Amorphous resins such as acrylic resin have been frequently used. However, since these are weak against plasticizers and activators, a protective layer is required on the surface of the charging roller in order to prevent these from seeping out. Further, since the protective layer is applied by dissolving the material in an organic solvent, there is a problem of environmental pollution.

Since the structure is complicated as described above, the charging roller is inevitably expensive, and it is difficult to regenerate the roller whose performance is deteriorated due to abrasion or the like, which also causes a cost increase. There is.

As the contact charging means, in addition to the above-mentioned roller, there is one utilizing a conductive brush as disclosed in Japanese Patent Laid-Open No. 242644-64. This type has the advantage that uniform charging is realized and the charging device does not wear against defects on the image carrier side, but on the other hand, since the contact pressure of the brush to the image carrier is low, Foreign matter is likely to enter the charged area, which causes charging failure. Also,
Since the fiber material forming the brush falls off and the surface of the fiber is apt to be an oxide generated at the time of discharge, the life is limited and regeneration is also difficult.

As still another charging means, Japanese Patent Laid-Open No. 1-9
Japanese Patent No. 3760 has been proposed in which the edge of an electrically conductive elastic blade is rubbed against the image carrier by press contact, but such an object has a narrow charging area and influences when foreign matter is involved. Is large, and since the image carrier is continuously rubbed by the blade edge, it is significantly worn and cannot be repaired and reused.

Therefore, it is an object of the present invention to use a charging roller as a charging means for an image carrier of an image forming layer, the charging roller as a whole is made of a single material, and the material of this portion is used. It is an object of the present invention to provide a charging member that has a simple structure, can be reused, is advantageous in cost, and does not cause environmental pollution by appropriately setting the crystallinity.

As described above, the contact type charging means such as the charging roller, the charging brush, and the charging blade as described above is used in order to combine several kinds of materials and to perform and maintain a desired function. In addition, an additional mechanism was required to increase the mounting accuracy, and the manufacturing process became complicated, which inevitably resulted in increased costs. Further, in the case of the type such as the charging blade that is not driven by the running of the image carrier, fine toner, paper dust, etc., which have slipped through the cleaner are likely to be accumulated in the charging area, which may cause charging failure.

That is, another object of the present invention is to elastically abut a charging member having a conductive layer and a resistance layer made of a polymer material on the image carrier at a non-moving position, and to apply a fluorine compound to the resistance layer. An object of the present invention is to provide a low-cost charging member with a simple structure that disperses the particles to reduce friction and prevents foreign matters from accumulating in the charging area.

Still another object of the present invention is to provide a charging member which has a conductive layer and a resistance layer made of a polymer compound, and which is brought into contact with an image carrier in an immovable state, on the surface of the resistance layer facing the image carrier. The provision of the fluorine compound layer is to provide a charging member that can effectively prevent foreign matter from adhering to the charging region.

[0013]

Configuration of the Invention

In order to achieve the above-mentioned object, the present invention comprises a single resistance layer formed around a core metal, and is pressed against an image carrier at a charging member of an image forming apparatus. In the charging member, the resistance layer contains a polymer compound copolymerized from two or more kinds of monomers, and the crystallinity of the entire composition forming the resistance layer is 2% or more and 60% or less. Or a charging member having a resistance layer formed in the shape of an elastic sheet and contacting the image carrier of the image forming apparatus in a fixed state, and contacting at least the image carrier of the charging member. A fluorine compound in the form of particles is dispersedly disposed on the side so that it is exposed on the surface, or is formed into an elastic sheet shape, and a resistance that abuts the image carrier of the image forming apparatus in a fixed state. In a charging member with layers The image bearing member charging member is a charging member, characterized in that the thin layer made of a fluorine compound to contact with a side formed by arranged.

With this structure, the structure is simple and advantageous in terms of cost, and charging failure due to damage to the image carrier and adhesion of foreign matter is effectively prevented, and stable and uniform charging is performed for a long period of time. be able to.

[0015]

Description of Embodiments An embodiment of a roller-shaped charging member will be described. FIG. 1 is a front view showing an embodiment of a charging member, and a core metal 1 made of an appropriate conductive material such as stainless steel.
A resistance layer 2 formed in a single layer in the shape of a roller is arranged on the surface. FIG. 2 shows a case where this is mounted on an image forming apparatus. The core metal 1 is rotatably supported by bearings 3 and 3 which can be displaced in the vertical direction in the drawing by a supporting member (not shown).
The bearing 3 is always biased upward by a spring 4 so that the resistance layer 2 of the charging member is pressed against the image carrier 5.

In the apparatus as described above, a DC voltage or an oscillating voltage obtained by superimposing an AC on a DC is applied from one of the cores 1 to apply a voltage between the image carrier 5 and the roller-shaped resistance layer 2. The surface of the image carrier is charged by the discharge generated in the minute space.

FIG. 3 is a side view showing the contact between the image carrier 5 and the resistance layer 2 of the charging member. By applying the charging bias as described above, the image carrier and the charging member are separated from each other. The charge is injected in the contact portion, and the discharge is generated in the minute space E near the contact portion, and the charge is applied to the image carrier side. However, in the case of such an apparatus, the injected charge is negligible because the potential difference between the electrode and the image carrier is large.

In the charging member having such a resistance layer, in the present invention, the layer contains a polymer compound copolymerized from two or more kinds of monomers, and the layer is formed. The crystallinity of the entire composition is 2% or more and 60% or less.
When the crystallinity is more than 60%, the flexibility is insufficient, and a gap is apt to be formed between the crystallinity and the image carrier when it is pressed against the image carrier, and the dispersion of the conductive pigment described later for adjusting the volume low efficiency. Is likely to be uneven. If the crystallinity is less than 2%, the cohesive force is lost and the roller shape cannot be maintained.

By thus determining the crystallinity of the composition, the resistance layer 2 is flexible without using a plasticizer, and a gap is generated between the resistance layer 2 and the image carrier when it is pressed against the image carrier. Even when a charging bias is applied,
Since the resistance layer itself absorbs vibration, it has a function of preventing charging noise.

Further, since the non-crystallized portion also exists to a considerable extent, the dispersion efficiency of the conductive pigment is good, and no dispersion aid is required.

The copolymerized polymer compounds include ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methyl acrylate copolymer, ethylene-methacrylic acid copolymer, atactic polypropylene, propylene. Examples include butene-1 copolymer and copolymer polyester. A composition is used in which these are mixed with compatible polymer compounds so that the overall crystallinity falls within the above-mentioned value.

Since most of them are thermoplastic resins, a composition obtained by dispersing a predetermined amount of conductive pigment can be molded into a roller shape on the outer periphery of the core metal by hot pressing or injection molding. In this case, since no solvent is used in the manufacturing process, environmental pollution does not occur.

As can be seen from the above description, since the structure is simple, the manufacturing cost can be greatly reduced.
If the surface of the resistance layer is deteriorated due to abrasion or adhesion of foreign matter, it can be easily reused by polishing the surface by several microns to several tens of microns at a time. Can contribute to cost reduction and resource saving.

Next, the adjustment of the resistance value of the resistance layer 2 will be described. The resistance of the resistance layer is preferably 1 × 10 ⁶ to 1 × 10 ¹⁰ Ω 10 seconds after applying 10 V.

Titanium oxide, tin oxide, carbon black, carbon graphite, zinc oxide, nickel, aluminum, copper, silver and the like can be used as the conductive pigment for adjusting the resistance.

When the resistance of the resistance layer is lower than 1 × 10 ⁶ Ω,
Concentration (leakage) of current in the pinhole is easy to occur,
On the other hand, when it exceeds 1 × 10 ¹⁰ Ω, the applied voltage is distributed in the resistance layer (voltage drop), and the chargeability of the image carrier is deteriorated.

The resistance layer 2 has a thickness of 50 to 5000 μm.
It is preferable that it is m. When the thickness is 50 μm or less, even if the resistance is within a predetermined range, when a voltage of 1 kv or more is applied, the resistance member does not function and uniform discharge cannot be performed. If there are pinholes on the image carrier, leakage will occur. On the other hand, when the thickness is 5000 μm or more, the resistance value becomes large and a voltage drop occurs to cause charging failure.

Next, concrete examples for carrying out the present invention will be described. A paper feeding experiment was conducted by mounting the above charging roller on the primary charging portion of the image forming apparatus as schematically shown in FIG. Each member of the image forming apparatus, the developing device D
Since the configurations, operations, and the like of E, the transfer roller CR, and the cleaner CL are well known, their description will be omitted. "Example 1" E as a resistance layer 2 on a core metal 1 having a diameter of 6 mm
Polyethylene 10 to VA (vinyl acetate content 30%)
Parts by weight and 70 parts by weight of conductive titanium oxide (total crystallinity 20%, resistance 7.0 × 10 ⁸ Ω) are molded by hot pressing to a thickness of 3 mm (outer diameter 12 mm) and charged. The roller was formed.

As shown in FIGS. 2 and 3, this charging roller was placed in pressure contact with the image carrier at the primary charging portion. The pressing force at this time was 10 g when the force when pulling out the 0.1 mm aluminum foil sandwiched between the both was measured.
r.

In this apparatus, a charging bias in which 1.8 Kv (voltage between peaks) and an alternating voltage with a frequency of 150 Hz are superposed on a direct current voltage of -550 V via a core metal 1 is applied, and a standard environment (23.C, 55) is applied. % RH), low temperature and low humidity environment (15.C, 10% RH), high temperature and high humidity environment (32.5.
In each environment of C, 85% RH), the image and the fusion of the toner after the initial passage of 3000 sheets were observed, and at the same time, the surface potential of the image carrier was measured. In addition, the leak due to the pinhole of the image bearing member was measured under a high temperature and high humidity environment.

Example 2 A composition in which 10 parts by weight of polyethylene and 70% by weight of conductive titanium oxide were mixed with EEA (ethyl acrylate content 20%) as a resistance layer in a core metal having a diameter of 6 mm (total crystal 15% conversion, 4.0 resistance
× 10 ⁸ Ω) was attached to a thickness of 3 mm and molded by hot pressing to form a charging roller. Using this, a paper passing experiment was conducted under the same conditions as in Example 1 above.

Example 3 A composition in which 5 parts by weight of polyethylene and 70 parts by weight of conductive titanium oxide were mixed with EMA (methyl acrylate content: 25%) as a resistance layer in a core metal having a diameter of 6 mm (total crystal) 10% chemical resistance, 3.0 × 10 resistance
⁹ Ω) was attached to a thickness of 3 mm and hot pressed to form a charging roller. Using this, a paper passing experiment was conducted under the same conditions as in Example 1 above.

Example 4 A composition in which 5 parts by weight of polyethylene and 30 parts by weight of conductive carbon black were mixed with EVA (vinyl acetate content 40%) as a resistance layer in a core metal having a diameter of 10 mm (total crystal) 5% resistance, 2.0 × resistance
A thickness of 1 mm (outer diameter 12 mm) was attached to 10 ⁶ Ω) and molded by hot pressing to form a charging roller. Using this, a paper passing experiment was conducted under the same conditions as in Example 1 above.

[Example 5] A composition in which 5 parts by weight of polyethylene and 30 parts by weight of conductive carbon black were mixed with EVA (35% pinyl acetate content) as a resistance layer in a core metal having a diameter of 2 mm (total crystal) 5% resistance, 5.0 × 10 resistance
⁹ Ω) was attached to a wall thickness of 5 mm (outer diameter 12 mm) and molded by hot pressing to form a charging roller. Using this, a paper passing experiment was conducted under the same conditions as in Example 1.

[Example 6] A core metal having a diameter of 6 mm was mixed with 20 parts by weight of polypropylene and 30 parts by weight of conductive carbon black in polypropylene-butene 1 copolymerization (butene 1 content 50%) as a low resistance layer. Of the composition (15% crystallinity, resistance 2.0 × 10 ⁸ Ω) with a wall thickness of 3 mm (outer diameter 1
2 mm) and molded by hot pressing to form a charging roller. Using this, a paper passing experiment was conducted under the same conditions as in Example 1.

The results of the above experimental examples are shown in FIG. As you can see, in each environment, 30
Good results were obtained and no pinhole leak was observed in any case after passing 00 sheets.

Further, the charging roller after the completion of paper feeding is taken out, and the surface layer thereof is 0.1 mm in Example 1, 1 mm in Example 2, 2 mm in Example 3, and 0.5 m in Example 4.
m, 4.9 mm in the fifth embodiment, 2.95 m in the sixth embodiment.
Each sheet was polished, and a 3000-sheet passing experiment was conducted again. The results are shown in the table of "Fig. 6".

Example 7 Next, EVA (vinyl acetate content 30%) was used as a resistance layer around a core metal having a diameter of 6 mm.
10 parts by weight of polyethylene and 70 parts of conductive titanium oxide
A composition (partial crystallinity 20%, resistance 7.0 × 10 ⁸ Ω) mixed in parts by weight was adhered to a thickness of 3 mm (outer diameter 12 mm) and molded by hot pressing to form a charging roller.

This is attached to the charging position of the image forming apparatus,
The contact force when pressed against the image bearing member is 1 when the force when pulling out with the aluminum foil sandwiched between them is measured with a spring balance.
It was 0 g.

Only a direct current voltage of 1200 V is applied to this charging roller to standard environment (23.C, 55% RH), low temperature and low humidity environment (15.C, 10% RH), high temperature and high humidity environment (3
2.5. C, 85% RH) initial 3000
The image after sheet passing and the fusion of toner were observed. Further, the surface potential of the image bearing member at each time point and the leak to the pinhole drum under high temperature and high humidity environment were tested. The surface of the image carrier and the charge transport layer were made of acrylic resin. The results are shown in the table of "Fig. 7".

Next, a comparative example will be described. All experimental conditions were the same as in the case of Example 1 above.

Comparative Example 1 A composition in which 10 parts by weight of polyethylene and 40 parts by weight of conductive titanium oxide were mixed with EVA (vinyl acetate content 30%) as a resistance layer on the outer circumference of a core metal having a diameter of 6 mm (total Crystallinity 20%, resistance 3.0 × 1
0 ¹¹ Ω) was attached to a wall thickness of 3 mm (outer diameter 12 mm) and molded by hot pressing to perform an experiment as a charging roller.

Comparative Example 2 A composition in which 10 parts by weight of polyethylene and 90 parts by weight of conductive titanium oxide were mixed with EVA (vinyl acetate content 30%) as a resistance layer on the outer circumference of a core metal having a diameter of 6 mm (total) Crystallinity 20%, resistance 1.5 × 1
An experiment was carried out as a charging roller by heat-pressing 0. ⁵ Ω) to a wall thickness of 3 mm (outer diameter 12 mm).

"Comparative Example 3" A composition in which 5 parts by weight of polyethylene (EMA) (25% methyl acrylate content) as a resistance layer and 50 parts by weight of conductive acid or titanium were blended on the outer periphery of a core metal having a diameter of 2 mm ( Overall crystallinity 10%, resistance 5.0
An experiment was carried out as a charging roller by depositing ¹⁰ × 10 ¹⁰ Ω) with a thickness of 5 mm (outer diameter 12 mm) and molding it with a hot press.

Comparative Example 4 On the outer circumference of a core metal having a diameter of 12 mm, EVA (vinyl acetate content 30%) was used as a resistance layer in an amount of 10 parts by weight of polyethylene and 65 parts by weight of conductive titanium oxide. Crystallinity of 20%, resistance 1.5
An experiment was carried out by injection-molding (× 10 ⁸ Ω) to a thickness of 40 μm to form a charging roller.

Comparative Example 5 A composition in which 80 parts by weight of conductive titanium oxide was mixed with PBT (polybutylene terephthalate) as a resistance layer on the outer periphery of a core metal having a diameter of 6 mm (total crystallinity 75%, resistance 1. 5 × 10 ⁸ Ω) was attached to a wall thickness of 3 mm (outer diameter 12 mm), and an experiment was conducted using a charging roller formed by injection molding.

Comparative Example 6 A composition prepared by blending 1 part by weight of polyethylene and 70 parts by weight of conductive titanium oxide in EVA (vinyl acetate content 80%) as a resistance layer on the outer circumference of a core metal having a diameter of 6 mm. Crystallinity 1%, resistance 3.0 × 10 ⁸
Ω) was attached to a thickness of 3 mm and formed by hot pressing. However, in this case, the composition had no cohesive force and could not maintain the shape of the roller.

The experimental results of the above comparative example are shown in the table of FIG. When the volume resistivity was larger than 1 × 10 ¹⁰ Ωcm, the surface potential of the image bearing member was too low, resulting in a fogged image with toner adhered to the entire surface. Further, when the volume low efficiency is less than 1 × 10 ⁶ Ωcm, the surface potential of the image carrier is greatly disturbed and uniform charging cannot be performed.

In Comparative Example 4, the resistance was within the predetermined range, but the bed thickness was too thin to function as a resistor.
The potential was greatly disturbed and uniform charging could not be performed. Comparative Example 5
Then, the resistance layer is too hard and a gap is generated between the resistance layer and the image carrier,
Again, uniform charging was impossible. Comparative Examples 1 to 1 above
With regard to 4, just by performing an initial evaluation under each environment,
The evaluation after passing the paper could not be performed.

Next, an embodiment in which a fluorine compound is dispersed in the charging member will be described.

FIG. 9 is a schematic side view showing a portion where the charging member is in contact with the image carrier of the image forming apparatus. An elastic charging member 12 is pressed against the image carrier 5, and the charging member 12 has a resistance layer 13 and an electrode layer (conductive tape) 14.
The resistance layer 13 is pressed against the image carrier 5 by its own elasticity.

Since the elastic material is pressed against the image bearing member by its own elasticity in this way, by setting the elasticity of the resistance layer appropriately, a uniform and appropriate pressure contact force can be obtained over the entire length (direction perpendicular to the paper surface). Since a special mechanism for maintaining the pressure contact force is not required, the structure is simple and space is saved, and it is also effective for cost reduction.

The resistance layer 13 has a structure in which a fluorine compound is dispersed in a suitable elastic polymer material together with a conductive pigment for resistance value adjustment, as shown in an enlarged view in a two-dot chain line frame in FIG. It is configured.

Due to such a constitution, the fluorine compound particles appear on the surface of the image bearing member side to form fine irregularities, thereby suppressing the frictional resistance between the resistance layer and the image bearing member as small as possible. In addition, it is possible to prevent adhesion of toner, paper dust, etc. that have slipped through the cleaning portion.

The volume resistivity of the resistance layer 13 is 1 × 10.
It is preferably about ⁶ to 1 × 10 ¹⁰ Ωcm. If the volumetric low efficiency is smaller than the above, current concentration (leakage) on the pinholes is likely to occur, and if the volume resistivity is larger than the above, the applied voltage is distributed within the resistor and a voltage drop occurs, resulting in an image. The chargeability of the carrier decreases.

The resistance layer is formed by dispersing a conductive pigment and a fluorine compound in a polymer compound and coating the conductive layer, a conductive compound-like conductive pigment having a molding property and a compound of the fluorine compound, and then extrusion molding or injection molding. It can be formed by means such as filming or sheeting. Since the resistance layer is required to have a uniform thickness, it is preferable to use a film or sheet.

The conductive pigment for adjusting the resistance value of the resistance layer can be selected from carbon black, carbon graphite, tin oxide, zinc oxide, titanium oxide, nickel, aluminum, copper, silver and the like.

The thickness of the resistance layer is 50 to 5000 μm.
If the thickness is less than 50 μm, even if the resistance value is within the predetermined range, it does not function as a resistance layer and uniform charging cannot be performed, and if a pinhole exists in the image carrier, leakage occurs. To do. When the thickness exceeds 5000 μm, the applied voltage is distributed in the resistance layer to cause a voltage drop, resulting in charging failure, or excessive pressure contact with the image carrier to hinder rotation of the image carrier. Excessive scraping of the photosensitive layer causes defective charging.

The amount of the fluorine compound dispersed in the resistance layer 13 is preferably 3 to 30 parts by weight. When the amount is less than 3 parts by weight, the amount of the fluorine compound exposed on the surface of the image bearing member is too small, the friction with the image bearing member becomes large, and the stick slip cannot be prevented. If the amount of the fluorine compound exceeds 30 parts by weight, the amount of the fluorine compound exposed on the surface is too large and the surface irregularities become large, and a gap is generated between the surface of the image bearing member and the surface of the charging member to obtain uniform charging. In addition to disappearing, the fluorine compound particles may fall off and cause new contamination.

Next, the result of an experiment conducted by mounting the charging member according to the embodiment of the present invention on the primary charging portion of the image forming apparatus having the structure shown in FIG. 4 will be described.

As shown in "Example 1" and "Fig. 9", a charging member having a conductive layer attached to a resistance layer was used, and the resistance layer was NBR (nitrile-butadiene-rubber).
To 30 parts by weight of conductive carbon black, PTFE powder 5
By dispersing parts by weight, the volume resistivity is 5.0 × 10 ⁷ Ωcm.
The sheet prepared as described above was used as a sheet having a thickness of 500 μm, and a conductive tape was attached to the back surface to obtain a charging member.

The contact pressure with the image carrier at this time was 10 g. A DC voltage of -550V and an AC voltage of a peak voltage of 1.8Kv and a frequency of 150Hz are superimposed and applied to the charging member, and under the same standard, high temperature, high humidity, and low temperature, low humidity environments as in the above-described embodiment. Images at the initial stage and after passing 3000 sheets, and fusion of toner were observed, and the surface potential of the image bearing member was measured and a leak test was conducted.

[Example 2] As the resistance layer, used was one prepared by dispersing 60 parts by weight of conductive titanium oxide and 10 parts by weight of PTFE powder in NBR and adjusting the volume resistivity to 7.5 x 10 ⁶ Ωcm. A conductive tape was attached to the back surface as a sheet having a thickness of 500 μm, and paper was passed as a charging member under the same conditions as in Example 1.

[Example 3] As the resistance layer, one prepared by dispersing 80 parts by weight of conductive tin oxide and 20 parts by weight of FEP powder in NBR and adjusting the volume resistivity to 1.0 x 10 ⁸ Ωcm was used. As a sheet having a thickness of 1000 μm, a conductive tape was attached to the back surface, and as a charging member, paper was passed under the same conditions as in Example 1.

Example 4 As a resistance layer, 35 parts by weight of conductive carbon black and 25 parts by weight of PFA powder were dispersed in EPDM (ethylene-propylene-dimonomer) to obtain a volume resistivity of 2.5 × 10 ⁷ Ωcm. The sheet prepared as described above was used as a sheet having a thickness of 500 μm, a conductive tape was attached to the back surface thereof, and the sheet was used as a charging member, and paper was passed under the same conditions as in Example 1.

Example 5 As the resistance layer, EPDM in which 65 parts by weight of conductive titanium oxide and 30 parts by weight of PTFE powder were dispersed to adjust the volume resistivity to 3.5 × 10 ⁶ Ωcm was used. A sheet having a thickness of 2000 μm was used as a charging member by attaching a conductive tape on the back surface of Example 1
The paper was passed under the same conditions as above.

[Example 6] As the resistance layer, EPDM in which 70 parts by weight of conductive tin oxide and 25 parts by weight of PTFE powder were dispersed to adjust the volume resistivity to 8.0 x 10 ⁷ Ωcm was used. This was used as a sheet having a thickness of 4000 μm and a conductive tape was attached to the back surface to form a charging member, and the paper was passed under the same conditions as in Example 1.

The experimental results of the respective examples are shown in FIG.
Shown in the table.

Next, the results of the paper feeding experiment of the comparative example are shown in the table of FIG. The evaluation methods were all the same as in Example 1.

[Comparative Example 1] As the resistance layer, one prepared by dispersing 20 parts by weight of conductive carbon black in NBR and adjusting the volume resistivity to 4.0 × 10 ⁷ Ωcm was used.
A conductive tape was attached to the back surface as a 00 μm sheet to form a charging member. In this case, there is no dispersion of the fluorine-based substance.

[Comparative Example 2] As the resistance layer, a material prepared by dispersing 10 parts by weight of conductive carbon black and 20 parts by weight of PTFE powder in NBR and adjusting the volume resistivity to 2.0 × 10 ⁹ Ωcm was used. As a sheet having a thickness of 500 μm, a conductive tape was attached to the back surface to obtain a charging member.

"Comparative Example 3" As a resistance layer, 50 parts by weight of conductive carbon black and 20 parts of PTFE powder were added to NBR.
One having a volume resistivity of 1.0 × 10 ⁵ Ωcm adjusted to be dispersed by weight was used, and this was used as a film having a thickness of 30 μm, and a conductive tape was attached to the back surface to obtain a charging member.

[Comparative Example 4] As the resistance layer, EPDM in which 70 parts by weight of conductive titanium oxide and 5 parts by weight of PTFE powder were dispersed to adjust the volume resistivity to 2.0 × 10 ⁷ Ωcm was used. As a film having a thickness of 30 μm, a conductive tape was attached to the back surface to form a charging member.

Comparative Example 5 As a low resistance layer, 70 parts by weight of conductive tin oxide was dispersed in EPDM to obtain a volume resistivity of 1.0.
Use the one adjusted to × 10 ⁹ Ωcm,
A conductive tape was attached to the back surface as a 00 μm sheet to form a charging member. In this case, no fluorine compound was mixed.

Since Comparative Example 1 contains no fluorine compound, the image is good, but stick-slip cannot be prevented. In Comparative Example 2, the volume resistivity was too high and no image was produced. In Comparative Example 3, the volume resistivity was too low, the surface potential of the image carrier was greatly disturbed, and leakage occurred at the pinhole portion of the image carrier. In Comparative Example 4, the resistance layer was too thin to act as resistance, and in this case also, the disturbance of the surface potential of the image carrier became large. In Comparative Example 5, the resistance layer was too thick and the contact pressure with the image bearing member became excessive, resulting in toner fusion.

Next, an embodiment of the charging member in which the elastic member made of a fluorine compound is brought into pressure contact with the image carrier will be described.

FIG. 12 is a side view of an essential part showing this embodiment, in which the charging member 1 is attached to the rotating cylindrical image carrier 5.
5 is shown elastically abutting. The charging member 15 is affixed to a resistance layer 18 made of a suitable elastic polymeric material, a thin layer 16 made of a fluorine compound which is on the image carrier side and is in contact with the resistance layer 18, and a side opposite to the image carrier. It is composed of an electrode layer (conductive tape) 17.

The charging member is disposed at the primary charging portion of the image carrier, and is in pressure contact with the image carrier mainly by the elasticity of the resistance layer 18. Therefore, the charging member 1
5 can be uniformly pressed against the image carrier over its entire length and does not require a spring or other special member or mechanism for pressing at a predetermined pressure, and the image carrier at a constant pressure for a long period of time. Since there is no possibility of damaging the image bearing member or fusing of the toner, the uniform charging is secured.

The resistance layer 18 is formed by dispersing a conductive pigment in a polymer compound and coating it, compounding the pigment in the polymer compound for molding, and then pelletizing it, and forming it into a sheet or film by means of extrusion molding, injection molding or the like. It is formed in such a way as to be converted. Since the resistance layer is required to have a uniform thickness, it is formed into a sheet,
It is preferable to use a film.

As the pigment for adjusting the resistance of the resistance layer 18, carbon black, carbon graphite, tin oxide, zinc oxide, titanium oxide, nickel, aluminum,
Copper, silver, etc. can be used.

The volume resistivity of the resistance layer is 1 × 10 ⁶ to 1 × 1.
It is preferably in the range of 0 ¹⁰ Ωcm. Volume resistivity is 1
When it is lower than × 10 ⁶ Ωcm, current concentration (leakage) easily occurs in the pinhole, and the volume resistivity is 1 ×.
When it exceeds 10 ¹⁰ Ωcm, the charging property is deteriorated due to the voltage drop.

Further, the resistance layer 18 has a thickness of 50 to 500.
The range of 0 μm is preferable. When the thickness is 50 μm or less, current is concentrated and leakage easily occurs when there is an image carrier side pinhole. On the other hand, if the thickness exceeds 5000 μm, charging failure due to voltage drop may occur, elasticity may become so strong that braking is likely to occur in rotational traveling of the image carrier, and the surface photosensitive layer may be damaged.

The thin layer 16 made of a fluorine compound is formed by coating a water-emulsified fluorine rubber, an amorphous fluorine resin dissolved in a perfluoro solvent, or the like by a spray method, a dip coating method, a spin coating method or the like. . Or PTFE, PFA, FEP, PC
A fluorine compound such as TE, PVF, ETFE, and ECTFE may be formed into a film and attached on the resistance layer.

The thickness of the thin layer is preferably about 1 to 10 μm. If it is less than 1 μm, it is easily consumed by friction with the image carrier, and if it exceeds 10 μm, the resistance becomes large and charging failure may occur.

Next, specific examples will be described, and the experimental results (Examples 1 to 6) are shown in the table of FIG.

Example 1 As a resistance layer, 30 parts by weight of carbon black was dispersed in NBR to obtain a volume resistivity of 5.0.
After adjusting to × 10 ⁷ Ωcm, it is used by forming it into a sheet with a thickness of 500 μm, coating the surface with fluoroelastomer that has been emulsified in water and coating it with a thickness of 3 μm, and then attaching a conductive tape on the back side to charge The member was constructed.

The charging member as described above is connected to the charging portion of the image forming apparatus as shown in FIG.
At the position (R position), the image bearing member was placed in pressure contact. The contact pressure at this time was 10 g.

To this charging member, an alternating voltage having a peak-to-peak voltage of 1.8 Kv and a frequency of 150 Hz was superimposed on DC-550V and applied, and the paper was passed under the same standard, high temperature, high pressure, and low temperature, low pressure environments as described above. At the initial stage, the images after the passage of 3000 sheets and the fusion of the toner were observed, and the surface potential of the image carrier was measured. In addition, the leak due to the pinhole of the image bearing member under the high temperature and high humidity environment was tested.

Example 2 As a resistance layer, 60 parts by weight of titanium oxide was dispersed in NBR to obtain a volume resistivity of 7.5 × 1.
A sheet having a thickness of 500 μm adjusted to 0 ⁶ Ωcm was used. A non-crystalline fluororesin was coated on the front surface of the perfluoro solvent by a spray method to a thickness of 5 μm (film thickness after drying), and a conductive tape was attached to the back surface to form a charging member. Paper was passed by this charging member under the same conditions as in Example 1.

Example 3 As a resistance layer, 80 parts by weight of conductive tin oxide was dispersed in NBR to obtain a volume resistivity of 1.0.
The one adjusted to × 10 ⁸ Ωcm was used. This is thickness 1
000μm sheet, 5μm thick PF on the surface
A film was attached, and a conductive tape was attached to the back surface to form a charging member. Using this charging member, paper was passed under the same conditions as in Example 1.

Example 4 As the resistance layer, EPDM in which 35 parts by weight of conductive carbon black was dispersed to adjust the volume resistivity to 2.5 × 10 ⁷ Ωcm was used. This is a sheet with a thickness of 500 μm, and the surface has a thickness of 8 μm.
The FEP film of 1 was attached, and the conductive tape was attached to the back surface to form a charging member. Paper was passed under the same conditions as in Example 1 using this charging member.

Example 5 As the resistance layer, EPDM in which 65 parts by weight of conductive titanium oxide was dispersed to adjust the volume resistivity to 3.5 × 10 ⁶ Ωcm was used. This was formed into a sheet with a thickness of 500 μm and the surface was made into a water-emulsion fluororubber by a bar coating method with a thickness of 8 μm.
(The film thickness after drying) was coated, and a conductive tape was attached to the back surface to obtain a charging member. Paper was passed under the same conditions as in Example 1 using this charging member.

Example 6 As a resistance layer, 70 parts by weight of conductive tin oxide was dispersed in EPDM to obtain a volume resistivity of 8.
The one adjusted to 0 × 10 ⁷ Ωcm was used. This was made into a sheet having a thickness of 1000 μm, and the surface was coated with an amorphous fluororesin dissolved in a perfluoro solvent to a thickness of 2 μm (film thickness after drying) by a dip coating method, and a conductive tape was attached to the back surface to form a charging member did. Paper was passed by this charging member under the same conditions as in Example 1.

Next, a comparative example will be described. In each of the following examples, paper is fed under the same conditions as in the above-mentioned Example 1,
The results are shown in the table of "Fig. 14".

Comparative Example 1 As a resistance layer, 20 parts by weight of conductive carbon black was dispersed in NBR to adjust the volume resistivity to 5.0 × 10 ⁷ Ωcm, and the thickness was 500 μm.
After the sheet was formed into a sheet, a conductive tape was attached to the back surface and paper was passed as a charging member. In this case, the film layer of the fluorine compound was not formed.

"Comparative Example 2" A resistance layer was prepared by dispersing 30 parts by weight of conductive carbon black in NBR and adjusting the volume resistivity to 5.0 x 10 ⁷ Ωcm. This was used as a sheet having a thickness of 500 μm, a FEP film having a thickness of 15 μm was attached to the front surface, and a conductive tape was attached to the back surface to form a charging member.

[Comparative Example 3] As the resistance layer, one prepared by dispersing 30 parts by weight of conductive carbon black in NBR and adjusting the volume resistivity to 5.0 × 10 ⁷ Ωcm was used. This was used as a sheet having a thickness of 500 μm, an amorphous fluororesin dissolved in a perfluoro solvent was formed on the surface by dip coating to a thickness of 0.5 μm (film thickness after drying), and a conductive tape was attached to the back surface. The charging member was used.

"Comparative Example 4" As a resistance layer, EPDM in which 40 parts by weight of conductive titanium oxide was dispersed to adjust the volume resistivity to 2.0 × 10 ¹¹ Ωcm was used, and this was formed into a sheet having a thickness of 500 μm. Formed. A non-crystalline fluorocarbon resin was applied to this surface by a dip coating method in a perfluoro solvent to coat it to a thickness of 3 μm (film thickness after drying), and a conductive tape was attached to the kneading surface to obtain a charging member.

Comparative Example 5 As a resistance layer, 70 parts by weight of conductive tin oxide was dispersed in EPDM to obtain a volume resistivity of 6.5.
The film adjusted to × 10 ⁵ Ωcm was used as a film having a thickness of 40 μm. A non-crystalline fluororesin was added to a perfluoro solvent on this surface by dip coating to a thickness of 3 μm.
m (film thickness after drying) was coated, and a conductive tape was attached to the back surface to obtain a charging member.

From the above results, good results were obtained in all of Examples 1 to 6. In Comparative Example 1, the resistance was in a good range, so that good results were obtained in the standard, low temperature and low humidity environment, but in the high temperature and high humidity environment, streaks were generated along the rotation direction of the image bearing member. This is because the foreign matter adhered like the resistance layer absorbs moisture under high temperature and high humidity, and the resistance of the part locally becomes low,
This is probably because the unevenness of the discharge occurred and the surface potential of the image carrier was disturbed.

In Comparative Example 2, it is considered that the thickness of the fluorine compound layer was excessively large and the resistance was too large to inhibit the discharge.

In Comparative Example 3, since the fluorine compound layer was too thin, it was ground during the paper passing test, and streaks were generated in the high temperature and high humidity environment as in Comparative Example 1.

In Comparative Example 4, it is considered that the resistance of the resistance layer itself was too large to cause a voltage drop and sufficient discharge was not performed.

In Comparative Example 5, the resistance of the resistance layer was too small to cause uneven discharge, and uniform charging could not be performed.

In Comparative Examples 2, 3 and 4 described above, only the initial evaluation was carried out and the evaluation after passing the paper could not be carried out.

[0106]

As described above, according to the present invention, the resistance layer of the charging roller which is disposed in contact with the image carrier of the image forming apparatus is made of a copolymer of two or more kinds of monomers. Since the composition is a single layer containing a molecular compound and having a crystallinity of 2 to 60% as a whole, a gap may be formed between the composition and the image bearing member without using a special plasticizer. Even if an oscillating electric field is applied, the charging roller itself absorbs the vibration to prevent the generation of charging noise. Further, since it has an amorphous portion, the dispersibility efficiency of the pigment for resistance adjustment is high and a dispersion aid is not required. Further, even if the roller surface is contaminated or damaged, it can be easily regenerated by grinding the surface, which is advantageous in terms of cost.

Furthermore, the present invention provides a charging member comprising particles of a fluorine compound dispersed in an elastic sheet-like resistance layer of a polymer compound, or a thin layer of the fluorine compound in the resistance layer. Since the charging member formed by the above is pressed against the image carrier by the elasticity of the charging member, the configuration of the charging device part including the auxiliary mechanism is extremely simple, and the elasticity of the resistance layer is appropriately set. By so doing, toner fusion can be effectively prevented, and a predetermined contact pressure can be stably maintained for a long period of time.

[Brief description of drawings]

FIG. 1 is a front view showing the configuration of a charging roller according to the present invention.

FIG. 2 is a front view showing a state in which a charging roller is placed in contact with an image carrier as above.

[Fig. 3] Side view of the above

FIG. 4 is a schematic side view of the image forming apparatus showing a mode of mounting a charging roller.

FIG. 5 is a diagram showing the results of a paper passing experiment using a charging roller as above.

FIG. 6 is a diagram showing a result of a paper passing experiment using a roller obtained by polishing and reproducing the charging roller of the same as above.

FIG. 7 is a diagram showing a paper feeding experiment of a charging roller that is an embodiment of the present invention.

FIG. 8 is a diagram showing a paper feeding experiment of a charging roller as a comparative example.

FIG. 9 is a schematic side view showing the vicinity of a charging portion of an image forming apparatus having a charging member according to another embodiment of the present invention.

FIG. 10 is a diagram showing a result of a paper feeding experiment using the charging member.

FIG. 11 is a chart showing a result of a paper feeding experiment of a charging member as a comparative example.

FIG. 12 is a schematic side view showing the vicinity of a charged portion of an image forming apparatus provided with a charging member according to still another embodiment of the present invention.

FIG. 13 is a diagram showing the results of a paper passing experiment using the charging member as above.

FIG. 14 is a chart showing the results of a paper feeding experiment of a charging member as a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 core metal 2 resistance layer 3 spring 5 image carrier 12, 15 charging member 13, 18 resistance layer 14, 17 conductive tape 16 fluororesin

Claims (5)

[Claims] 1. A single resistance layer is formed around a core bar,
In a charging member of an image forming apparatus, particularly in a charging member which is brought into pressure contact with an image carrier, the resistance layer contains a polymer compound copolymerized from two or more kinds of monomers, and a composition forming the resistance layer. A charging member having a crystallinity of 2% or more and 60% or less as a whole. 2. The charging member according to claim 1, wherein the charging member is formed in a roller shape in which a resistance layer is arranged on a cored bar. 3. A charging member, which is formed in the shape of an elastic sheet and has a resistance layer that comes into contact with the image carrier of the image forming apparatus in a fixed state, wherein at least the side of the charging member that comes into contact with the image carrier is particulate. 2. A charging member, characterized in that the fluorine compound is dispersed and arranged so as to be exposed on the surface. 4. A charging member having a resistive layer formed in the shape of an elastic sheet and having a fixed contact with an image carrier of an image forming apparatus, wherein a fluorine compound is formed on the side of the charging member contacting the image carrier. A charging member, characterized in that a thin layer is formed. 5. The charging member according to claim 3, wherein the resistance layer is made of a polymer compound.