JPH11218995A - Charging member and electrophotographic apparatus using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a charging member high in quality and durability and low in cost by incorporating a styrene type elastomer and an amide type elasto mer specified in a mixing ratio in a surface layer. SOLUTION: The charging roller comprises a conductive core metal 2a and an elastic layer 2b of a conductive rubber or the like formed into roller-shape concentrically by molding on the core metal 2a and a surface layer 2d formed on the circumference of the layer 2b, and, when needed, further an intermediate layer (C) is provided between the elastic layer 2b and the surface layer 2d. The surface layer 2d comprises the styrene type elastomer and the amide type elastomer in an amide type amount of 5-70 pts. per mass of the styrene type. The stryene type elestomer is embodied by a block copolymer of polystyrene and polybutadiene or polyisoprene.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member used in an electrophotographic image forming apparatus and an electrophotographic apparatus using the same.

[0002]

2. Description of the Related Art An electrophotographic apparatus such as an electronic copying machine and an electrostatic recording apparatus includes a step of uniformly charging an object to be charged.
As a charging method, a corona charging method is generally used. However, the corona charging method often generates products such as ozone, and requires additional means and a mechanism to cope with the problem. There is a problem that it is easy to increase the size and cost.

Therefore, recently, a contact charging method has been studied as a new charging method replacing the corona charging method, and some of them have been put to practical use.

In the contact charging method, a charging member to which a voltage is applied is brought into contact with a charged body with a predetermined pressing force to charge the charged body. Since the generation of ozone is greatly reduced as compared with the corona charging method, there is an advantage that the corona charging method does not require any additional means and mechanism. As the applied voltage, a superimposed voltage of a DC voltage and an AC voltage having a peak-to-peak voltage that is about twice the charging start voltage when the DC voltage is applied to the charging member is often used.

The charging member is usually provided with a conductive support, a conductive elastic layer formed of a rubber or a foam formed around the conductive support, and further improved thereon, for example, abrasion resistance and photoreceptor contamination resistance. Depending on the purpose, etc., a structure provided with one or more conductive coating layers is often used.

Means for providing a conductive coating layer and the like include: 1) a method in which a paint having conductivity is coated thinly by dipping, spraying or the like; 2) a tube formed into a tube having conductivity is coated or And extrusion molding directly on the elastic layer.

[0007]

However, the current charging member manufactured by the above method has the following problems. (A) When the means for providing a conductive coating layer or the like is coating 1) Since the material must be dissolved in a solvent to form a paint, there are restrictions on the materials used.

2) Since the manufacturing process is complicated as compared with the tube coating, the manufacturing cost is increased.

3) It is difficult to finish the surface smoothly as compared with tube coating. In particular, when a foam is used for the support member, it is easily affected by unevenness on the surface. If the surface smoothness is insufficient, charging may be uneven and image defects may occur, or drum scraping may increase due to an increase in the discharge amount. (B) Case Where Means for Providing Conductive Coating Layer and the Like is Tube Coating and the Like For example, Japanese Patent Application Laid-Open No. 5-2313 discloses a seamless tube made of a fluororesin.

[0010] Fluororesins have the following disadvantages, although they have advantages such as better environmental stability, better non-stickiness and non-staining properties and better durability stability than other resins.

1) The material cost of the fluororesin itself is high, and the adhesiveness is poor, so that the inner surface of the tube needs to be etched, and the cost reduction effect by simplifying the process is surprisingly small.

2) Fluororesins generally have high hardness. Inevitably, the surface hardness of the charging member is increased, and there is a possibility that the developer is fused on the surface of the photoconductor.

[0013] 3) The fluororesin is not easily elastically deformed, and the tube may be torn or the wall thickness may be uneven due to a large force generated at the time of joining.

4) It is difficult for the fluororesin to uniformly disperse the conductive pigment to be added for the purpose of resistance adjustment, which may cause insufficient charging uniformity and image defects.

Further, Japanese Patent Application Laid-Open No. 6-58325 discloses a method in which various thermoplastic resins are directly molded on a conductive elastic layer using a crosshead extruder. According to this method, since the surface layer can be formed by a simple process, the cost can be greatly reduced. However, the following problems occur depending on the selection of the material.

For example, 1) polyamide-based and polyester-based elastomers generally have disadvantages such as high hardness, easy occurrence of image defects due to toner fusion during use, high water absorption and poor environmental stability. 2) Polystyrene-based and polyolefin-based elastomers have very few polar groups in the molecular structure, making it difficult to uniformly disperse the added conductive material for resistance adjustment. There is.

3) Polyurethane-based elastomers have high water absorption and are inferior in environmental stability. They decompose and reduce the molecular weight due to the effects of heat applied during molding, temperature and humidity during use, etc., which contaminate the photoreceptor and deteriorate its properties. May worsen. And other problems.

An object of the present invention is to provide a high-quality, high-durability, low-cost charging member and an electrophotographic apparatus using the same without the above-mentioned problems.

[0019]

That is, the present invention provides a charging member having at least a conductive elastic layer and a surface layer, wherein the surface layer contains a styrene-based elastomer and an amide-based elastomer. A charging member characterized in that the mixing amount of the amide-based elastomer with respect to parts by weight is 5 parts by weight or more and 70 parts by weight or less.

Styrene-based elastomers can be reduced in cost in terms of materials and production, such as being excellent in moldability and low raw material unit price. In addition, it has advantages such as low water absorption, excellent environmental stability, and low hardness, which does not cause image defects due to fusion of toner to a photoreceptor.

However, as a disadvantage, as described above, it is difficult to uniformly disperse the conductive pigment to be added for the purpose of adjusting the resistance, and as a result, the uniformity of charging becomes insufficient and image defects may occur. .

To solve this problem, the inventors of the present invention have conducted intensive studies, and as a result, it has been found that by mixing an amide-based elastomer with a styrene-based elastomer in an appropriate amount, the dispersibility of the conductive agent is dramatically improved. As a result, a charging member and an electrophotographic apparatus using the same, which can achieve both high quality, high durability, and low cost, which were the objects of the present invention, could be obtained.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the styrene elastomer includes a block copolymer of polystyrene and polybutadiene, a block copolymer of polystyrene and polyisoprene, polystyrene and polyethylene,
Examples include block copolymers with polybutylene, block copolymers with polystyrene and polyethylene, polybutylene, and olefin crystals. Among them, especially the block copolymer of polystyrene and polybutadiene, the block copolymer of polystyrene and polyethylene, polybutylene, and olefin crystals have very small tackiness,
When used as a surface material, it is suitable for reasons such as little sticking to the photoreceptor and little adhesion of fouling substances such as toner and paper powder.

Examples of the amide-based elastomer include those having nylon 6, nylon 66 or nylon 12 as a hard segment and polyether or polyester as a soft segment. Among them, nylon 12 has low water absorption (nylon 6
/ Nylon 12 = approximately 7/1), which is suitable because of relatively good environmental stability.

The above-mentioned styrene-based elastomer and amide-based elastomer may be used alone or in combination of two or more.

The mixing amount of the amide elastomer with respect to 100 parts by weight of the styrene elastomer of the present invention is 5-7.
0 parts by weight, preferably 10 to 50 parts by weight. If the amount is less than 5 parts by weight, the effect is insufficient. If the amount is more than 70 parts by weight, the hardness of the surface layer of the charging member is inevitably increased because the ester-based elastomer generally has high hardness. Toner fusion is likely to occur. Further, since the amide-based elastomer has a high raw material unit price, the cost of the charging member also increases.

The hardness of the surface of the charging member of the present invention is preferably 90 degrees or less, more preferably 8 degrees or less.
5 degrees or less. When the angle is 90 degrees or more, although the charging characteristics are good, fusion of the toner or the like to the member to be charged is apt to occur, which may cause an image defect. Therefore, it is necessary to use an amide-based elastomer having a relatively low hardness for the surface layer. The surface hardness is a value measured by a micro rubber hardness meter manufactured by Kobunshi Keiki Co., Ltd.

These polymer compounds used for the surface layer include:
A conductivity-imparting agent, a lubricant, a curing agent, and other additives may be added. Examples of the conductivity-imparting agent include carbon black, graphite, metal oxides such as titanium oxide, tin oxide, and zinc oxide, and metal powders such as gold, silver, copper, and nickel. You may use individually or in combination of 2 or more types.

As a method of forming the surface layer, a tube-shaped material is coated by an appropriate means such as molding or extrusion. At this time, when the tube has heat shrinkability, the tube can be coated by making the inside diameter larger than the support, inserting the support into the tube, and then heat shrinking the tube. When the tube does not have heat shrinkability, the tube may be made smaller in inner diameter than the support, and may be inflated with an appropriate means such as air and then fitted.

In the present invention, a conductive elastic layer may be provided if necessary.

For the conductive elastic layer, for example, ethylene propylene rubber (EPDM), nitrile rubber (NBR),
Styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), chloroprene rubber (CR), acrylic rubber (ACM), silicone rubber,
Rubber materials such as fluoro rubber, polystyrene,
Any of polystyrene, polyvinyl chloride, polyurethane, polyamide, polyamide, and thermoplastic elastomers can be used.

The elastic layer may be made of either a solid or a sponge, but a sponge is preferable from the viewpoint of reducing charging noise.

The conductive elastic layer preferably has a volume resistivity value of preferably 10 ^{2 to} 10 ¹⁰ Ωcm, more preferably 10 ^{3 to} 10 ⁹ Ωcm. 10 ² Ω
If it is less than cm, it may be difficult to control the resistance required for the charging member. Further, not only is it uneconomical because a large amount of a conductivity-imparting agent is required, but also the hardness of the base material can be extremely high even when, for example, a highly conductive carbon black is used. Also 10
^If it exceeds ¹⁰ Ωcm, it may be difficult to obtain the resistance required for forming a charging member exhibiting good charging characteristics.

FIG. 1 is a schematic structural view of an example of an image forming apparatus using the charging member of the present invention.

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 rotates at a predetermined peripheral speed (process speed) in a clockwise direction indicated by an arrow. Driven. 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 parallel to the surface of the photosensitive drum 1 and in contact with a predetermined pressing force. Then, the photosensitive drum 1 is driven to rotate.

As shown in FIG. 2, the charging roller 2 of this embodiment includes a conductive core 2a and an elastic layer 2b of a conductive rubber or the like which is formed concentrically and integrally with the core in a roller shape by molding or the like. And a surface layer 2d formed on the outer periphery thereof. Further, if necessary, an intermediate layer c can be provided between the elastic layer 2b and the surface layer 2d. In the charging roller 2 of the present embodiment, the above-described polymer compound is used for a surface layer 2d which is a 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 from the power supply to the metal core 2 a of the charging roller 2, the peripheral surface of the rotating photosensitive drum 1 has a predetermined polarity and potential. It is charged by a contact charging method.

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

The surface of the photosensitive drum 1 which has been subjected to the primary charging process uniformly at 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 The steps of toner development and transfer of the formed toner image to the transfer material 7 by the transfer means 6 are sequentially performed, and the transfer material 7 that has been transferred from the surface of the photosensitive drum 1 after receiving the toner image is introduced into a fixing means (not shown). It is output as an image formed product (print). After the transfer of the toner image, the surface of the photosensitive drum 1 is cleaned by a cleaning device 8 to remove adhered and contaminated matter of toner remaining after transfer, and is repeatedly used for image formation.

[0041]

Embodiments will be described below.

Example 1 [Preparation of Elastic Layer] 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,
1 part by weight of a vulcanization accelerator MTB, 1 part by weight of a vulcanization accelerator TMTD, 1.5 parts by weight of a vulcanization accelerator ZnMDC, and 10 parts by weight of a foaming agent (sodium bicarbonate) were mixed for 20 minutes while cooling with two rolls. A compound was made.

The above compound was heated and foamed and vulcanized at 150 ° C. for 15 minutes on a stainless steel cored bar having a diameter of 6 mm to obtain a sponge roller having an elastic layer having a thickness of 3 mm.

[Production of Surface Layer] 100 parts by weight of a styrene elastomer (styrene / butadiene / styrene block copolymer) and an amide elastomer (nylon 1
2 / polyester block copolymer) 30 parts by weight
Knead in advance at 80 ° C for 5 minutes. 90 parts by weight of this mixture and 10 parts by weight of conductive carbon were melt-kneaded at 180 ° C. for 10 minutes in a pressure kneader, cooled and pulverized, and then pelletized using a single-screw extruder. Further, a seamless tube having an inner diameter of 11.5 mm and a thickness of about 150 μm was produced from the pellets using a twin-screw extruder.

[Preparation and Evaluation of Charging Roller] Air was blown into the inside of the surface layer tube to expand the inner diameter, and then the elastic layer was inserted to obtain a charging member. It was 70 degrees when the micro hardness of the surface was measured.

This charging roller is attached to the primary charging position of a cartridge used for a laser beam printer (manufactured by LaserJet 4si Hewlett-Packard), and a DC voltage of −750 V, an AC voltage of 2.0 kV (peak-to-peak voltage) and a bias of a frequency of 650 Hz are applied. Low humidity environment (15 ° C-10% RH),
Initial image evaluation and a durability test of 8000 sheets were performed in a high humidity environment (32.5 ° C.-80% RH). Table 1 shows the results.

(Example 2) [Preparation of elastic layer] Same as in Example 1 [Preparation of surface layer] The same method as in Example 1 was used except that 100 parts by weight of styrene-based elastomer and 5 parts by weight of amide-based elastomer were used. , Inner diameter is 11.5mm, wall thickness is about 15
A 0 μm seamless tube was produced.

[Preparation and Evaluation of Charging Roller] A charging member was obtained in the same manner as in Example 1. The micro hardness of the surface was 60 degrees.

This charging roller was evaluated in the same manner as in Example 1. Table 1 shows the results.

(Example 3) [Preparation of elastic layer] Same as in Example 1 [Preparation of surface layer] The same method as in Example 1 was used except that 100 parts by weight of styrene-based elastomer and 70 parts by weight of amide-based elastomer were used. , Inner diameter is 11.5mm, wall thickness is about 1
A 50 μm seamless tube was produced.

[Preparation and Evaluation of Charging Roller] A charging member was obtained in the same manner as in Example 1. The micro hardness of the surface was 90 degrees.

This charging roller was evaluated in the same manner as in Example 1. Table 1 shows the results.

(Example 4) [Preparation of elastic layer] Same as in Example 1 [Preparation of surface layer] The same method as in Example 1 was used except that 100 parts by weight of styrene-based elastomer and 10 parts by weight of amide-based elastomer were used. , Inner diameter is 11.5mm, wall thickness is about 1
A 50 μm seamless tube was produced.

[Preparation and Evaluation of Charging Roller] A charging member was obtained in the same manner as in Example 1. The micro hardness of the surface was 65 degrees.

This charging roller was evaluated in the same manner as in Example 1. Table 1 shows the results.

(Example 5) [Preparation of elastic layer] Same as in Example 1 [Preparation of surface layer] The same method as in Example 1 was used except that 100 parts by weight of styrene-based elastomer and 50 parts by weight of amide-based elastomer were used. , Inner diameter is 11.5mm, wall thickness is about 1
A 50 μm seamless tube was produced.

[Preparation and Evaluation of Charging Roller] A charging member was obtained in the same manner as in Example 1. The micro hardness of the surface was 80 degrees.

This charging roller was evaluated in the same manner as in Example 1. Table 1 shows the results.

(Comparative Example 1) [Preparation of elastic layer] Same as in Example 1 [Preparation of surface layer] The same method as in Example 1 except that only 100 parts by weight of the styrene-based elastomer was used.
A seamless tube having a thickness of 1.5 mm and a thickness of about 150 μm was produced.

[Preparation and Evaluation of Charging Roller] A charging member was obtained in the same manner as in Example 1. The micro hardness of the surface was 55 degrees.

This charging roller was evaluated in the same manner as in Example 1. Table 1 shows the results.

(Comparative Example 2) [Preparation of elastic layer] Same as in Example 1 [Preparation of surface layer] The same method as in Example 1 was used except that 100 parts by weight of styrene-based elastomer and 3 parts by weight of amide-based elastomer were used. , Inner diameter is 11.5mm, wall thickness is about 15
A 0 μm seamless tube was produced.

[Preparation and Evaluation of Charging Roller] A charging member was obtained in the same manner as in Example 1. The micro hardness of the surface was 58 degrees.

This charging roller was evaluated in the same manner as in Example 1. Table 1 shows the results.

(Comparative Example 3) [Preparation of elastic layer] Same as in Example 1 [Preparation of surface layer] The same method as in Example 1 except that 100 parts by weight of styrene-based elastomer and 90 parts by weight of amide-based elastomer were used. , Inner diameter is 11.5mm, wall thickness is about 1
A 50 μm seamless tube was produced.

[Preparation and Evaluation of Charging Roller] A charging member was obtained in the same manner as in Example 1. The micro hardness of the surface was 95 degrees.

This charging roller was evaluated in the same manner as in Example 1. Table 1 shows the results.

[0068]

[Table 1]

[0069]

As described above, the present invention relates to a charging member having at least a conductive elastic layer and a surface layer,
The surface layer contains a styrene-based elastomer and an amide-based elastomer.
By using the charging member, wherein the mixing amount of the amide-based elastomer with respect to 0 parts by weight is 5 parts by weight or more and 70 parts by weight or less, excellent in quality and durability when used in an electrophotographic image forming apparatus. In addition to exhibiting the above characteristics, a low-cost charging member can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of an example of an image forming apparatus using a charging member according to the present invention.

FIG. 2 is a longitudinal sectional view showing an example of a charging member according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging roller 2a Core metal 2b Elastic layer 2c Intermediate layer 2d Surface layer 3 Voltage application power supply 4 Image exposure means 5 Developing means 6 Transfer means 7 Transfer material 8 Cleaning means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 77:12) (72) Inventor Hiroshi Koyama 3- 30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Invention Person Seiji Tsuru 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Hiroyoshi Suzuki 3-30-2 Shimomaruko 3-chome, Ota-ku, Tokyo Inside Canon Inc. (72) Hiroshi Inoue Tokyo 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (6)

[Claims] 1. A charging member having at least a conductive elastic layer and a surface layer, wherein the surface layer contains a styrene-based elastomer and an amide-based elastomer. A charging member characterized in that the amount is from 5 parts by weight to 70 parts by weight. 2. The charging member according to claim 1, wherein the styrene-based elastomer is a block copolymer of polystyrene and polyethylene, polybutylene, or an olefin crystal. 3. The charging member according to claim 1, wherein the styrene elastomer is a block copolymer of polystyrene and polybutadiene. 4. The charging member according to claim 1, wherein the amide-based elastomer has nylon 12 as a hard segment. 5. The charging member according to claim 1, wherein the micro hardness of the surface of the charging member is 90 degrees or less. 6. An electrophotographic apparatus having a photosensitive member, a latent image forming unit, a unit for developing the formed latent image, and a unit for transferring the developed image to a transfer material, wherein the photosensitive member is charged as the latent image forming unit. 6. Any one of claims 1 to 5 for processing
An electrophotographic apparatus using the charging member according to the above item.