JPH11184209A - Electrifying member and electrophotographic device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain uniform electrification for a long time by using a material in which thermoplastic polyurethane elastomer is incorporated by adequate amount in thermoplastic polyamide elastomer for a surface layer. SOLUTION: An electrifying roller being a contact electrifying member is a multilayer structure constituted of the conductive elastic layer 2b of conductive rubber, etc., concentrically and integrally formed in a roller state on a conductive core bar by injection molding, etc., and a conductive surface layer 2c formed on the outside periphery of the layer 2b. Besides, an intermediate layer is provided between the layers 2b and 2c at need. As to this electrifying roller, a thermoplastic elastomer material incorporating the thermoplastic polyamide elastomer and the thermoplastic polyurethane elastomer is used for the surface layer 2c being a material layer brought into contact with the surface of the photoreceptor drum which is a body to be electrified. By this constitution, adequate hardness can be obtained and the body to be electrified can be uniformly electrified for a long time.

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 an electrophotographic apparatus using the same. More specifically, the present invention relates to a charging member for applying a voltage to charge a surface of an object to be charged to a predetermined potential, and an electrophotographic apparatus having the same.

[0002]

2. Description of the Related Art Conventionally, many methods are known as electrophotography. In general, a photoconductive substance is used to form an electric latent image on a photoreceptor by various means. The image is developed with a powder developer (toner) into a visible image,
After the toner image is transferred to a transfer material such as paper as required, the toner image is fixed on the transfer material by heat, pressure, or the like to obtain a copy. Further, toner particles remaining on the photoconductor without being transferred onto the transfer material are removed from the photoconductor by a cleaning process.

[0003] Conventionally, as a charging device for electrophotography,
Corona chargers using corona chargers have been used. In recent years, a contact charging device has been put to practical use instead. The contact charging device has advantages that a lower voltage can be used, the amount of generated ozone is small, and the device can be downsized, as compared with the corona charging device. Among them, a roller charging method using a conductive roller as a charging member is preferably used in the contact charging device from the viewpoint of charging stability.

FIG. 1 shows a configuration example of a contact charging device using a charging roller. In the roller charging method, a conductive elastic roller (charging roller) 1 is brought into pressure contact with a photoreceptor 2 to be charged, and a voltage is applied thereto to charge the photoreceptor surface. Reference numeral 3 denotes a voltage application power source, 4 denotes an image exposure unit, 5 denotes a development unit, 6 denotes a transfer unit, 7 denotes a transfer material,
Reference numeral 8 denotes a cleaning device.

More specifically, since the charging is performed by discharging from the charging member to the member to be charged, the charging is started by applying a voltage equal to or higher than a certain threshold voltage. For example, when a charging roller is pressed against an OPC photosensitive member having a thickness of 25 μm, the surface potential of the photosensitive member starts to increase when a voltage of about 650 V or more is applied. On the other hand, the photoconductor surface potential increases on a straight line having a slope of 1. Hereinafter, this threshold voltage is defined as a charging start voltage Vth.

That is, a DC voltage of Vth + Vd is required for the charging roller in order to obtain the photoconductor potential Vd required for electrophotography. The method of applying only a DC voltage to the contact charging member to charge the photosensitive member to a predetermined potential in this manner is generally called DC charging.

However, in DC charging, the resistance value of the contact charging member fluctuates due to environmental fluctuation or the like, or the film thickness fluctuates and the Vth fluctuates due to the shaving of the photoconductor, so that the surface potential of the photoconductor is changed. Was difficult to obtain a desired value.

For this reason, as described in Japanese Patent Application Laid-Open No. 63-149669, a DC voltage corresponding to a desired photosensitive member surface potential Vd is applied to further uniform charging.
A so-called AC charging method is used in which a superimposed voltage with an AC voltage having a peak-to-peak voltage of twice or more than th is applied to the contact charging member. This is for the purpose of determining whether or not the potential of the AC voltage is equalized. The potential of the photoconductor converges to Vd, which is the median of the peaks of the AC voltage, and is not affected by disturbances such as the environment. .

Next, an example of a configuration as a contact charging member will be described.

FIG. 2 is a schematic sectional view of the charging roller. The charging roller includes a conductive elastic layer 2b necessary for forming a uniform contact portion with the member to be charged on a conductive support (core bar) 2a, and further has abrasion resistance and resistance to the elastic layer. For the purpose of improving the photoreceptor properties, a configuration having a conductive surface layer 2c is used. The conductive elastic layer 2b and the conductive surface layer 2c may be used as necessary to adjust resistance or prevent exudation.
In some cases, a configuration in which a conductive intermediate layer is provided therebetween is adopted.

The conductive elastic layer 2b is made of EPDM, SBR,
A conductive agent such as conductive carbon black is dispersed in synthetic rubber such as NBR and silicone rubber.

The surface layer 2c has a structure in which a conductive agent such as conductive carbon black, conductive tin oxide, or conductive titanium oxide is dispersed in a synthetic resin such as polyamide, polyurethane or fluorine for resistance adjustment. .

For example, as disclosed in JP-A-1-205180, attempts have been made to form N-alkoxymethylated nylon on the surface layer of a charging roller. However, in the case of this configuration, since the material has high water absorbency and high moisture absorbability, there is a problem in that the material is strongly affected by the use environment, particularly humidity, and its resistance value changes. Therefore, in a high-temperature, high-humidity environment, the resistance is reduced by absorbing moisture, and if there is a defect such as a pinhole or a scratch on the surface of the charged body (photosensitive drum), a current leaks from the charging roller (so-called pinhole leak). As a result, the member to be charged is non-uniformly charged, causing image defects. On the other hand, in a low-temperature and low-humidity environment, there is a defect that the resistance is increased and an image defect (so-called sand fog) due to a charging failure occurs.

Japanese Patent Application Laid-Open No. Hei 5-2312 proposes a charging device having a surface member mainly composed of a polyamide resin having a saturated water absorption of 10% or less in water.

Japanese Patent Application Laid-Open No. Hei 6-308801 discloses a charging roller having a polyamide-polyol block copolymer provided on a surface layer.

[0016]

However, when the above-mentioned polyamide resin and polyamide-polyol block copolymer are used for the surface layer of a charging roller, conductive carbon black, conductive titanium oxide, etc. are used for the purpose of resistance adjustment. When the conductive agent is added, the hardness tends to increase. Therefore, there is a drawback that, due to this, the powder developer (toner) is fused to the surface of the photoreceptor and an image defect occurs. That is, when the above materials are used, there is a problem that it is difficult to achieve both resistance and hardness.

It is an object of the present invention to solve the above-mentioned problems and to provide a charging member capable of obtaining uniform charging over a long period of time and an electrophotographic apparatus using the same.

[0018]

In order to solve this problem,
As a result of intensive studies, the present inventors have found that, by using a material in which a thermoplastic polyamide elastomer contains an appropriate amount of a thermoplastic polyurethane elastomer for a surface layer, a charging member capable of obtaining uniform charging over a long period of time and a use thereof. Was realized.

[0019]

That is, the present invention is a charging member characterized in that the surface layer contains at least a thermoplastic polyamide elastomer and a thermoplastic polyurethane elastomer.

The above thermoplastic polyamide elastomer comprises:
Nylon 6, Nylon 66, Nylon 11, Nylon 1
2 and a polyether component (soft segment) such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

Above all, from the viewpoint of reducing the environmental fluctuation of the resistance value of the charging member, it is preferable to use a thermoplastic polyamide elastomer containing nylon 11 or nylon 12 having low hygroscopicity as the polyamide component.

Examples of the thermoplastic polyurethane elastomer include a reaction product of an isocyanate compound and a polyol. As the isocyanate compound,
4,4-methylenebis (phenyl isocyanate),
Examples thereof include 1,6-hexamethylene diisocyanate, 2,4-tolylene diisocyanate, isophorone diisocyanate, and hydrogenated 4,4-methylenebis (phenyl isocyanate). Examples of the polyol include polymer polyols such as diols of polyadipates, diols of polyalkylene ethers, diols of polylactone, diols of polycarbonate, and ethylene glycol, propylene glycol, 1,4-butanediol, 1,6- And low molecular weight polyols such as hexanediol and glycerin.

The mixing ratio of the thermoplastic polyamide elastomer of the present invention to the thermoplastic polyurethane elastomer is preferably 10 to 80 parts by weight of the thermoplastic polyurethane elastomer per 100 parts by weight of the thermoplastic polyamide elastomer.

If the mixing ratio of the thermoplastic polyurethane elastomer is 5 parts by weight or less, the effect may be insufficient in terms of lowering the hardness. On the other hand, if the amount of the thermoplastic polyurethane elastomer is 100 parts by weight or more, the slip property, which is an advantage of the thermoplastic polyamide elastomer, may be impaired, which may cause contamination of the charging member surface.

The thermoplastic polyamide elastomer and the thermoplastic polyurethane elastomer may be used alone or as a mixture of two or more.

As the compatibilizer, maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, maleic anhydride-allyl ether copolymer, maleic anhydride-grafted ethylene propylene rubber and the like may be added.

Further, for the purpose of adjusting the resistance of the conductive surface layer, a conductive agent can be added. Examples of the conductive agent include conductive carbon black, conductive carbon graphite, conductive titanium oxide, conductive tin oxide, metal oxides such as conductive zinc oxide, and metal powders such as gold, silver, copper, and nickel. These may be used alone or in combination of two or more. The resistance value of the conductive surface layer is preferably in the range of 1 × 10 ⁵ Ω · cm to 10 ¹¹ Ω · cm. If it is lower than 1 × 10 ⁵ Ω · cm, if there is a surface defect such as a pinhole or a scratch on the photosensitive drum, the current is concentrated and so-called pinhole leak occurs. On the other hand, if the resistance exceeds 1 × 10 ¹¹ Ω · cm, the applied voltage drops, and the chargeability of the photosensitive drum deteriorates, so-called sand fog occurs.

The hardness of the conductive surface layer of the charging member of the present invention is preferably not more than 80 degrees as measured by an A-type tester in a spring hardness test specified in JIS K6301. When the hardness is 90 degrees or more, although the chargeability is good, fusion of the powder developer (toner) or the like to the photoreceptor is likely to occur, which may cause an image defect.

As a method of forming the conductive surface layer, first, a predetermined amount of a thermoplastic polyamide elastomer, a thermoplastic polyurethane elastomer and a conductive agent are dry-mixed using a Henschel mixer, a V-type blender, and a cylindrical blender, and then pressurized. Melt kneading is performed using a kneader such as a kneader or an extruder. Further, pelletization into a predetermined shape is performed by an extruder and a pelletizer. Next, it is formed into a tube by an extruder equipped with a predetermined tube forming die. As a method for forming a tube, a molding method such as free extrusion, vacuum extrusion, pressure sizing, and internal calibration can be used.

The obtained tubular conductive surface layer is coated on the conductive elastic layer. When the tube has heat shrinkability, it can be coated by forming the inner diameter larger than the outer diameter of the conductive elastic layer, inserting the conductive elastic layer into the tube, and then heat shrinking the tube. In addition, when it does not have heat shrinkability, the inner diameter of the tube-shaped conductive surface layer is formed slightly smaller than the outer diameter of the conductive elastic layer, and after being expanded by appropriate means such as air or nitrogen gas, It can be coated on the conductive elastic layer.

Further, the conductive elastic layer of the charging member in the present invention is made of ethylene propylene rubber (EPDM), styrene butadiene rubber (SBR), butadiene rubber (B
R), isoprene rubber (IR), chloroprene rubber (C
R), synthetic rubber such as acrylic rubber (ACM), acrylonitrile butadiene rubber (NBR), silicone rubber, polyurethane, polystyrene, polyamide,
Solid or foamed materials such as thermoplastic elastomers such as polyester and polyvinyl chloride can be used.

For adjusting the resistance of the conductive elastic layer, a conductive agent that can be used for the conductive surface layer can be used. The resistance value of the conductive elastic layer is 1 × 10 ⁶ Ω · cm
The following is preferred. Resistance value is 1 × 10 ⁶ Ω · c
If it exceeds m, the applied voltage drops in the conductive elastic layer, and the chargeability of the photosensitive drum deteriorates.

Further, as the conductive support (core metal) of the present invention, a metal round bar of iron, copper, nickel, stainless steel, brass or the like may be used as it is, or the surface may be chemically coated for rust prevention. A surface treatment such as nickel plating or chrome plating may be performed, but it is necessary that the conductivity is not impaired.

FIG. 1 showing a schematic configuration of an electrophotographic apparatus using the charging member of the present invention will be described in more detail.

In FIG. 1, reference numeral 1 denotes a rotating drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) as a member to be charged, which is rotationally driven at a predetermined peripheral speed (process speed) in a clockwise direction indicated by an arrow. You. 1a is a conductive drum base made of aluminum or the like of the photosensitive drum 1, and 1b is a photosensitive layer formed on the outer peripheral surface of the drum base 1a.

Reference numeral 2 denotes a contact charging member. This embodiment is a roller body (hereinafter, referred to as a charging roller) which is disposed substantially in parallel with the surface of the photosensitive drum 1 and in contact with a predetermined pressing force. Then, the photosensitive drum 1 is driven to rotate.

The charging roller 2 comprises a conductive core 2a, a conductive elastic layer 2b of a conductive rubber or the like formed concentrically and integrally with the core by injection molding or the like, and a conductive core formed on the outer periphery thereof. It has a multi-layer structure composed of the conductive surface layer 2c.
Further, if necessary, an intermediate layer can be provided between the conductive elastic layer 2b and the conductive surface layer 2c. In the charging roller 2 of this embodiment, the above-mentioned thermoplastic elastomer material is used for the conductive surface layer 2c which is a material layer in contact with the surface of the photosensitive drum 1 which is a member to be charged.

Reference numeral 3 denotes a power supply for applying a voltage to the charging roller 2. By applying a predetermined voltage to the metal core 2 a of the charging roller 2 from the power supply, the outer peripheral surface of the rotating photosensitive drum 1 has a predetermined polarity and potential. It is charged.

The voltage applied to the charging roller 2 may be only a DC voltage, but a superimposed voltage (oscillation voltage) of a DC voltage and an AC voltage is applied to uniformly charge the surface of the photosensitive drum 1 as a member to be charged. Is more preferred.

The surface of the photosensitive drum 1 which has been uniformly primary-charged to a predetermined potential by the charging roller 2 is subjected to laser beam scanning exposure 4 of target image information by a laser scanner (image exposure means) (not shown), and a developing device 5 Are sequentially performed by the transfer means 6 of the formed toner image by the transfer means 6 on the transfer material (for example, paper), and the transfer material 7 separated from the surface of the photosensitive drum 1 by receiving the toner image is transferred.
Is introduced into a fixing unit (not shown) and output as an image molded product (print). Photosensitive drum 1 after transfer of toner image
The surface of the surface is cleaned by a cleaning device 8 to remove the contaminants adhering to the toner remaining after transfer, and the surface is repeatedly provided for image formation.

[0041]

The present invention will be described below with reference to examples.

(Example 1) [Preparation of conductive elastic layer] The following raw materials were mixed for 20 minutes using two rolls cooled to 20 ° C to prepare a compound.

EPDM: 100 parts by weight Zinc oxide: 5 parts by weight Higher fatty acid: 1 part by weight Conductive carbon black 5 parts by weight Paraffin oil 10 parts by weight Sulfur 2 parts by weight Vulcanization accelerator (MBT) 1 part by weight Vulcanization accelerator (TMTD) 1 part by weight Vulcanization accelerator (ZnMDC) 1.5 parts by weight Blowing agent (sodium bicarbonate)... 10 parts by weight Further, the above compound was heated and vulcanized at 150 ° C. for 30 minutes on the outer periphery of a stainless steel core bar having a diameter of 6 mm to obtain a thickness of 3
A foam roller (outer diameter: 12 mm) having an elastic layer of 1 mm was obtained. Next, when the electric resistance value of the present roller was measured at a temperature of 23 ° C. and a relative humidity of 60%, it was 0.05 MΩ. The measuring method is as follows. A 10 mm wide aluminum foil (thickness: 50 μm) is tightly wound around the outer periphery of the charging roller, and a DC voltage of 250 V is applied between the core metal and the aluminum foil to measure the resistance.
HIOKI 3119 DIGITAL MΩ HIT
ESTER (manufactured by Hioki Electric Co., Ltd.) was used.

[Preparation of Conductive Surface Layer] Thermoplastic polyamide elastomer (polyamide component; nylon 12, polyether component; polytetramethylene glycol, JIS
A hardness 92 degrees) 100 parts by weight, thermoplastic polyurethane elastomer (polyol component: polytetramethylene glycol, isocyanate component: 4,4-methylenebis (phenylisocyanate), JIS A hardness 60 degrees)
80 parts by weight and 8 parts by weight of conductive carbon black were dry-mixed with a Henschel mixer for 5 minutes. Then, the mixture was melt-kneaded at 190 ° C. for 10 minutes using a pressure kneader. After further cooling, the mixture was pulverized by a pulverizer and then pelletized by using a single screw extruder.

Further, a die having an inner diameter of 12 mm and an outer diameter of 11
Using a crosshead extruder with nipples of
A seamless tube having an inner diameter of 11.5 mm and a thickness of about 200 μm was obtained.

Further, using the same pellets, a sheet having a thickness of 2 mm was prepared by a hot press, and a spring type hardness tester A was prepared according to the method specified in JIS K6301.
It was 58 degrees when the hardness was measured by the shape.

[Preparation of Charging Roller] Air was blown into the seamless tube to enlarge the inner diameter of the tube.
A conductive elastic layer (foamed roller) was inserted, and the two were fitted together by the contraction force of the tube to obtain a charging roller.

Next, the electric resistance value of the charging roller was measured under a high temperature and high humidity environment (temperature of 32 ° C., relative humidity of 80%) and a low temperature and low humidity environment (temperature of 15 ° C., relative humidity of 10%).
The measuring method is as follows. A 10 mm-wide aluminum foil (50 μm thickness) is tightly wound around the outer periphery of the charging roller, a DC voltage of 250 V is applied between the core metal and the aluminum foil, and a resistance meter HI is used.
OKI 3119 DIGITAL MΩ HITES
TER (manufactured by Hioki Electric Co., Ltd.) was used.

This charging roller was used as a laser beam printer (manufactured by Canon Inc., trade name: LBP-8MarkI).
V) Process cartridge (product name; EP)
-E cartridge), DC voltage: -670 V DC voltage: 2000 V (peak-to-peak voltage) Frequency: 650 Hz superimposed voltage is applied from an external power supply to a low-temperature, low-humidity environment (temperature 15 ° C, relative An image durability test was performed in each environment of a humidity of 10%) and a high-temperature and high-humidity environment (temperature of 32 ° C., relative humidity of 80%) at a print ratio of 5% on 8000 sheets.
Image evaluation was carried out by visually observing the image obtained after 8,000 sheets of paper had been used.

In both the high temperature and high humidity environment and the low temperature and low humidity environment,
A good image was obtained even after 8000 sheets of durability. Table 1 shows the obtained results.

In the table, ○ indicates that the obtained image is good, Δ indicates that the image is practical, and X indicates that the image is not practical.

(Example 2) In Example 1, a thermoplastic polyurethane elastomer (polyol component: polytetramethylene glycol, isocyanate component: 4,4-methylenebis (phenylisocyanate)) in the conductive surface layer, JIS A hardness 50 degrees The charging roller of Example 2 was prepared in the same manner as in Example 1 except that the addition amount of ()) was changed to 60 parts by weight, and image evaluation was performed. Tables 1 and 2 show the results.
Shown in

In both a high temperature and high humidity environment and a low temperature and low humidity environment,
A good image was obtained even after 8000 sheets of durability.

Example 3 In Example 1, the thermoplastic polyurethane elastomer (polyol component: polytetramethylene glycol, isocyanate component: 4,4-methylenebis (phenylisocyanate)) in the conductive surface layer, JIS A hardness 50 degrees A charging roller of Example 3 was prepared in the same manner as in Example 1 except that the addition amount of ()) was changed to 40 parts by weight, and image evaluation was performed. Table 1 shows the results.

In both the high temperature and high humidity environment and the low temperature and low humidity environment,
A good image was obtained even after 8000 sheets of durability.

Example 4 In Example 1, a thermoplastic polyurethane elastomer (polyol component: polytetramethylene glycol, isocyanate component: 4,4-methylenebis (phenylisocyanate) in the conductive surface layer, JIS A hardness: 50 degrees The charging roller of Example 4 was prepared and evaluated in the same manner as in Example 1 except that the amount of ()) was changed to 20 parts by weight. Table 1 shows the results.

In both a high temperature and high humidity environment and a low temperature and low humidity environment,
A good image was obtained even after 8000 sheets of durability.

(Example 5) In Example 1, a thermoplastic polyurethane elastomer (polyol component; polytetramethylene glycol, isocyanate component; 4,4-methylenebis (phenylisocyanate)) in the conductive surface layer, JIS A hardness 50 degrees A charging roller of Example 5 was prepared and evaluated in the same manner as in Example 1 except that the amount of ()) was changed to 10 parts by weight. Table 1 shows the results.

In both high-temperature and high-humidity environments and low-temperature and low-humidity environments,
A good image was obtained even after 8000 sheets of durability.

(Example 6) In Example 1, 100 parts by weight of a thermoplastic polyamide elastomer (polyamide component; nylon 11, polyether component; polytetramethylene glycol, JIS A hardness 93 degrees) in the conductive surface layer, heat Example 1 except that a thermoplastic polyurethane elastomer (polyol component; polytetramethylene glycol, isocyanate component; 4,4-methylenebis (phenylisocyanate), JIS A hardness 60 degrees) was 60 parts by weight and conductive carbon black was 8 parts by weight. The charging roller of Example 5 was produced in the same manner as in Example 1 and evaluated. The results are shown in Tables 1 and 2.

In both a high temperature and high humidity environment and a low temperature and low humidity environment,
A good image was obtained even after 8000 sheets of durability.

(Example 7) In Example 1, 100 parts by weight of a thermoplastic polyamide elastomer (polyamide component; nylon 66, polyether component; polytetramethylene glycol, JIS A hardness 94 degrees) in the conductive surface layer, heat Example 1 except that a thermoplastic polyurethane elastomer (polyol component; polytetramethylene glycol, isocyanate component; 4,4-methylenebis (phenylisocyanate), JIS A hardness 60 degrees) was 60 parts by weight and conductive carbon black was 8 parts by weight. The charging roller of Example 5 was produced in the same manner as in Example 1 and evaluated. The results are shown in Tables 1 and 2.

In both a high temperature and high humidity environment and a low temperature and low humidity environment,
A good image was obtained even after 8000 sheets of durability.

Example 8 In Example 1, 100 parts by weight of a thermoplastic polyamide elastomer (polyamide component; nylon 6, polyether component; polytetramethylene glycol, JIS A hardness 94 degrees) in the conductive surface layer, heat Example 1 except that a thermoplastic polyurethane elastomer (polyol component; polytetramethylene glycol, isocyanate component; 4,4-methylenebis (phenylisocyanate), JIS A hardness 60 degrees) was 60 parts by weight and conductive carbon black was 8 parts by weight. The charging roller of Example 5 was produced in the same manner as in Example 1 and evaluated. The results are shown in Tables 1 and 2.

In both the high temperature and high humidity environment and the low temperature and low humidity environment,
A good image was obtained even on 8,000 sheets.

Comparative Example 1 Example 1 was repeated except that a tube (200 μm thick) in which 8 parts by weight of conductive carbon black was dispersed in 100 parts by weight of nylon 12 was used as the conductive surface layer. A charging roller of Comparative Example 1 was produced in the same manner as in Example 1. Table 1 shows the evaluation results.

In a high-temperature, high-humidity environment, more than ten white spots having a drum pitch (94 mm) due to fusion of the toner to the surface of the photosensitive drum were generated on the solid black image after 8,000 sheets of durability.

(Comparative Example 2) In Example 1, a thermoplastic polyamide elastomer (polyamide component; nylon 12, polyether component; polytetramethylene glycol, JIS A) was used without adding a thermoplastic polyurethane elastomer to the conductive surface layer. A charging roller of Comparative Example 2 was produced and evaluated in the same manner as in Example 1, except that the hardness was 92 degrees) and the conductive carbon black was 8 parts by weight. Table 1 shows the results.

In a high-temperature, high-humidity environment, more than tens of white spots having a drum pitch (94 mm) were generated on a solid black image after 8,000 sheets of durability due to fusion of toner to the surface of the photosensitive drum.

(Comparative Example 3) In Example 1, a thermoplastic polyurethane elastomer (polyol component: polytetramethylene glycol, isocyanate component: 4,4-methylenebis (phenylisocyanate), JIS A hardness 50 degrees) was used in the conductive surface layer. A charging roller of Comparative Example 3 was prepared and evaluated in the same manner as in Example 1, except that the amount of (3) was changed to 3 parts by weight. Table 1 shows the results.

In a high-temperature, high-humidity environment, more than ten white dots with a drum pitch (94 mm) due to fusion of the toner to the surface of the photosensitive drum were generated on the solid black image after 8,000 sheets of durability.

(Comparative Example 4) A thermoplastic polyurethane elastomer (polyol component: polytetramethylene glycol, isocyanate component: 4,4-methylenebis (phenylisocyanate), JIS A hardness 50 degrees) in the conductive surface layer in Example 1. A charging roller of Comparative Example 3 was prepared and evaluated in the same manner as in Example 1 except that the amount of (3) was changed to 5 parts by weight. Table 2 shows the results.

In a high-temperature, high-humidity environment, several white spots having a drum pitch (94 mm) due to fusion of the toner to the surface of the photosensitive drum were generated on the solid black image after 8,000 sheets of durability.

(Comparative Example 5) In Example 1, the thermoplastic polyurethane elastomer (polyol component: polytetramethylene glycol, isocyanate component: 4,4-methylenebis (phenylisocyanate), JIS A hardness: 50 degrees in the conductive surface layer A charging roller of Comparative Example 4 was prepared and evaluated in the same manner as in Example 1 except that the amount of ()) was changed to 100 parts by weight. Table 2 shows the results.

In a low-temperature and low-humidity environment, unevenness in the charging roller pitch (38 mm) due to charging roller contamination occurred on the halftone image after 8000 sheets of image durability.

Comparative Example 6 In Example 1, the thermoplastic polyurethane elastomer (polyol component: polytetramethylene glycol, isocyanate component: 4,4-methylenebis (phenylisocyanate)) in the conductive surface layer, JIS A hardness 50 degrees A charging roller of Comparative Example 5 was prepared and evaluated in the same manner as in Example 1 except that the amount of ()) was changed to 120 parts by weight. Table 1 shows the results.

In a low-temperature and low-humidity environment, unevenness in the charging roller pitch (38 mm) due to charging roller contamination occurred on the halftone image after 8000 sheets of image durability.
In addition, even in a high-temperature and high-humidity environment, density unevenness of the charging roller pitch (38 mm) caused by charging roller contamination occurred on the solid black image after 8000 sheets of durability.

[0078]

[Table 1]

[0079]

[Table 2]

[0080]

According to the present invention, since at least the surface layer contains a thermoplastic polyamide elastomer and a thermoplastic polyurethane elastomer, it has an appropriate hardness and is excellent in environmental stability. Therefore, the member to be charged can be uniformly charged over a long period of time.

1) It is possible to prevent the toner from fusing to the surface of the member to be charged (photosensitive drum).

2) Adhesion of toner to the surface of the charging member (charging roller) can be prevented.

3) Resistance variation due to the environment of the charging member is small.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of an electrophotographic apparatus using a charging member according to the present invention.

FIG. 2 is a schematic configuration diagram of a charging member of the present invention.

FIG. 3 is a diagram showing a method for measuring the resistance of the charging member of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 charging roller 1 a conductive drum substrate 1 b photosensitive layer 2 photosensitive drum 2 a conductive support (core metal) 2 b elastic layer 2 c surface layer 3 voltage application power supply 4 image exposure means 5 developing means 6 transfer means 7 transfer material 8 cleaning device 9 Aluminum foil 10 Resistance meter

Claims (5)

[Claims] 1. A charging member characterized in that the surface layer contains at least a thermoplastic polyamide elastomer and a thermoplastic polyurethane elastomer. 2. The thermoplastic polyamide elastomer 1
The charging member according to claim 1, wherein the content of the thermoplastic polyurethane elastomer is from 10 parts by weight to 80 parts by weight based on 00 parts by weight. 3. The thermoplastic polyamide elastomer according to claim 1, wherein the polyamide component comprises nylon 6, nylon 6, or the like.
The charging member according to claim 1, wherein the charging member is any one of 6, nylon 11, and nylon 12. 4. The surface hardness of the charging member is JIS K6.
In the spring hardness test specified in 301, A
The hardness measured by a shape tester is 80 degrees or less.
5. The charging member according to any one of 4. 5. An electrophotographic apparatus comprising a photoconductor, a latent image forming unit, a unit for developing a formed latent image, and a unit for transferring a developed image to a transfer material, wherein the latent image forming unit charges the photoconductor. An electrophotographic apparatus having the charging member according to claim 1 as a member to be charged.