JP3134464B2 - Conductive roll - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive roll for development, charging, static elimination and transfer used in an electrophotographic recording apparatus.

[0002]

2. Description of the Related Art An electrophotographic recording apparatus widely used in copiers, laser beam printers, and the like generally includes a drum-shaped photosensitive member (hereinafter, referred to as a photosensitive drum). The photosensitive drum is charged and exposed to form an electrostatic latent image, and then toner is adhered and developed according to the latent image on the photosensitive drum. Then, the photosensitive drum is discharged to a predetermined potential and the toner remaining on the photosensitive drum is cleaned to prepare for the next printing. Further, the toner carried on the recording medium by the transfer is fused and pressed to fix the toner on the recording medium, thereby completing a series of recording operations.

Charging means for applying a predetermined potential to the charged area of the photosensitive drum of the electrophotographic recording apparatus, transfer means for applying a predetermined potential to the recording medium conveyed to the transfer area, or Conventionally, a corona charging method has been used as a static eliminator for uniformizing the charged area of a photosensitive drum to a constant potential, in which a high voltage of several hundred to several thousand volts is applied to a thin wire to cause corona discharge. Is generally and widely used.

However, in the case of using such a corona charging method, active molecules such as ozone generated by corona discharge may deteriorate the photosensitive drum and other parts or adversely affect the human body. In addition, there is a problem in terms of risk of electric shock accidents due to high voltage, and maintenance management for wire contamination and disconnection.

Therefore, unlike such a corona charging method, a roller-type contact charger (hereinafter, referred to as a conductive roll) configured to apply a predetermined potential by bringing a conductive rubber roller into direct contact with a photosensitive drum. Has been proposed. This conductive roll is a high molecular weight nitrile butadiene rubber,
It is made of solid rubber such as chloroprene rubber, styrene-butadiene rubber, butadiene rubber, isoprene rubber, polynorbornene rubber, foamed rubber or urethane, and does not require a higher voltage than the corona-charged type, and has an activity such as ozone. It has excellent characteristics such as almost no generation of molecules.

In the case of such a charging system, the conductive roll obtains a predetermined electric resistance value, that is, the conductive roll obtains a predetermined voltage and applies a predetermined potential to a photosensitive drum or a recording medium to thereby perform a desired recording. In order to obtain the toner and to improve the contamination of the photosensitive drum due to the fusion of the toner to the photosensitive drum, a material having a higher resistance and a higher coefficient of friction than the rubber composition forming the conductive roll, for example, oxidation. The coating layer is formed on the surface of the conductive roll with a polymer material in which titanium is dispersed, but the electrical resistance fluctuates due to changes in the environment, such as temperature and humidity. Therefore, there is a problem that the conductive roll cannot obtain a desired resistance value, and thus cannot obtain a desired performance.

[0007] The present invention has been made in view of the above circumstances,
It is an object of the present invention to provide a conductive roll having low environmental resistance of electric resistance.

[0008]

The present inventors have made intensive studies to achieve the above object, and as a result, have found that a shaft having good conductivity and a conductive rubber layer (outer layer) provided on the outer periphery of the shaft have good conductivity. A coating layer provided on the outer periphery of the rubber layer and having a higher electrical resistance than the rubber layer, and having a predetermined polarity potential applied thereto while contacting the photosensitive member or the recording medium of the electrophotographic recording apparatus. A first coating layer formed on the rubber layer; a second coating layer formed on the first coating layer and having a higher resistance and a smaller film thickness than the first coating layer.
It has been found that it is effective to form a two-layer structure with the coating layer.

That is, the coating layer is necessary to obtain a desired resistance value as a conductive roll, but it is desired to increase the frictional resistance of the roll surface, that is, the coating layer, in order to improve the fusibility. Therefore, it is effective to form the coating layer with, for example, titanium oxide dispersed in a polymer material. However, a desired resistance value cannot be obtained simply by forming a polymer material. To obtain a desired resistance value, carbon black or the like is blended with a polymer substance on the conductive rubber layer (outer layer) to obtain a desired resistance value. 1) forming a coating layer, and blending a high molecular substance with titanium oxide or
It is effective to form a second coating layer having a higher resistance than the coating layer, and to make the thickness of the second coating layer having a higher resistance smaller than the thickness of the first coating layer, in particular, to reduce the thickness. 10μ
m or less, even if the second coating layer has a high resistance, it does not fluctuate due to the environment such as temperature and humidity, reduces the environment dependency of the conductive roll as a whole, It has been found that the frictional resistance can be increased and the fusing property of the toner to the photoreceptor can be improved. Further, in this case, by forming the rubber layer using a mixed rubber of liquid polyisoprene rubber and solid butadiene rubber, a conductive roll excellent in adhesion to the photosensitive drum and non-staining property can be obtained with good workability. This has led to the achievement of the present invention.

Hereinafter, the present invention will be described in more detail. The conductive roll of the present invention comprises a shaft having good conductivity, a conductive rubber layer provided on the outer periphery thereof, and a conductive rubber layer provided on the outer periphery of the rubber layer. A coating layer having a larger electrical resistance than the rubber layer,
In a conductive roll that applies a predetermined polarity potential to a photosensitive member or a recording medium of an electrophotographic recording device while contacting them, the rubber layer is a rubber layer containing liquid polyisoprene rubber and solid butadiene rubber, The coating layer,
A first coating layer formed on the rubber layer, and a second coating layer formed on the first coating layer and having a higher resistance and a smaller thickness than the first coating layer. is there.

FIG. 1 shows an example of the conductive roll of the present invention. This conductive roll is used as a charger of an electronic copying machine, and includes a shaft 1, a conductive rubber layer (outer layer).
2, a first coating layer 3 and a second coating layer 4.

Here, the good conductor forming the shaft 1 may be a metal such as steel, stainless steel, brass or the like, or a conductive plastic, but is not limited thereto.

The conductive rubber layer (outer layer) 2 is formed of a conductive rubber composition containing a conductive powder. In this case, a liquid polyisoprene rubber and a solid rubber are used as rubber components in the conductive rubber composition. Butadiene rubber is used.

[0014]

In this case, the liquid isoprene rubber includes:
Melt viscosity at 38 ° C (B-type viscometer, Tokyo Keiki Co., Ltd.)
Manufactured) 500-7000, average molecular weight (Mv) 200
It is preferably from 00 to 60000.

In the present invention, since the rubber layer is formed by combining the liquid polyisoprene rubber and the solid butadiene rubber, the adhesion to the photosensitive drum is high, and there is no possibility of contaminating the photosensitive drum. ) It is easy to make soft rubber with a rubber hardness of less than Asker C61. (2) Even if a large amount of liquid polyisoprene rubber (LIR) is blended in a large amount, adhesion to banbury or rolls is small. (3) Mold separation during vulcanization. Good properties such as (4) fast vulcanization, (5) little compression set during vulcanization, etc. can be imparted.

In order to more effectively exert such effects, the solid butadiene rubber is not particularly limited, but preferably contains 90% or more of a cis-1,4 structure.

The mixing ratio of the polyisoprene-based rubber to another rubber such as butadiene rubber is 10/90 by weight.
５０50/50, particularly preferably 20 / 80-40 / 60. If the proportion of the polyisoprene rubber is too small, the hardness of the vulcanized rubber may be too high, and if too large, the adhesive of the kneaded rubber may be too strong to be processed.

For the purpose of imparting conductivity, the conductive rubber composition may be provided with a conductive powder such as carbon black, graphite, metal, and various conductive metal oxides (such as tin oxide and titanium oxide), carbon fiber, and the like. Various conductive fibers such as short fibers of metal oxide are blended. The compounding amount of the conductive powder and the conductive fiber can be 20 to 100 parts by weight based on 100 parts by weight of the total rubber, whereby the resistance value of the rubber layer is 10 ³ to 10 ³ .
It can be formed to 10 ¹⁰ ρ · cm. The rubber composition forming the rubber layer 2 may further contain ordinary additives such as a filler, a vulcanizing agent, a vulcanization accelerator, a plasticizer, a dispersant, and a processing aid. And the rubber layer 2 having a thickness of 1 to 10 mm can be formed.

The conductive roll of the present invention applies a uniform electric potential to the photosensitive drum in order to improve the fusion of the toner to the photosensitive drum. It is preferable to polish in a barrel shape using a method such as the above. Due to this polishing, the outer diameter of the central portion of the rubber layer 2 becomes larger than the outer diameter of the end portion, and no lifting occurs in the central portion even when a load is applied to both ends when the roll is brought into close contact with the photosensitive drum. .

When the rubber layer 2 is further softened to improve the adhesion to the photosensitive drum,
30 minutes to 3 hours at a temperature of 0 ° C., preferably 180 to 210 ° C.
The heat treatment is preferably performed for a period of time, preferably 30 minutes to 2 hours. When performing the above-mentioned polishing, it is preferable to perform such a heat treatment after the polishing process.

Next, as the first coating layer 3 and the second coating layer 4, epichlorohydrin, acrylic rubber, silicone rubber, chlorosulfonated polyethylene, fluoroolefin vinyl ether copolymer, one-component or two-component polyurethane, It can be formed using various polymer substances such as N-methoxymethyl nylon, various nylons such as a copolymer of nylon and polyether, and polyester elastomers.

In this case, conductive carbon or the like is dispersed in the first coating layer 3, but the resistance value of the first coating layer 3 is 10 ⁶
It is preferably from 10 to 10 ¹⁰ ρ · cm, particularly preferably from 10 ⁷ to 10 ⁹ ρ · cm. The film thickness is 30 to 500 μm, especially 50
It is preferable to set it to 300 μm.

Titanium oxide or the like is dispersed in the second coating layer 4 in order to obtain a desired resistance value.
The resistance value of the coating layer 4 is 10 ⁷ to 10 ¹¹ ρ · cm, particularly 10 ⁶
It is preferably set to 〜１０10 ¹⁰ ρ · cm. The amount of titanium oxide or the like is 10% in the second coating layer 4 from the viewpoint of frictional resistance.
It is preferably set to 100% by weight, particularly 20 to 70% by weight. Further, the film thickness is preferably 10 μm or less, particularly preferably 1 to 8 μm.
m, particularly preferably 1 to 8 μm.

The dispersion of the particles is carried out by a shaker.
After the particles are dispersed, it is preferable to dry at a temperature of 100 to 150 ° C. within 3 hours. By adopting such a dispersion method and drying conditions, the frictional resistance of the roll surface can be increased, the electric resistance is less dependent on the environment, and it is effective in improving the fusion of the toner to the photosensitive drum. .

[0026]

The present invention will be described below in more detail with reference to Examples, but the present invention is not limited to the following Examples.

EXAMPLE A conductive rubber layer having a thickness of 3 m was formed on a steel shaft by using a conductive rubber composition having the following formulation.
m thickness.

Formulation of conductive rubber composition 60 parts by weight of cis-1,4-polybutadiene (BR02LL manufactured by Nippon Synthetic Rubber Co., Ltd.) 40 parts by weight of liquid polyisoprene (Kuraray isoprene LIR30 manufactured by Kuraray Co., Ltd.) Ketjen Black EC 10 Parts by weight Zinc white 10 parts by weight Sulfur 0.8 parts by weight Accelerator 0.7 parts by weight In addition, vulcanization conditions are 160 ° C. × 5 minutes, and after vulcanization, the surface of the conductive rubber layer is polished with a grindstone. The outer diameter of the portion was made larger than that of the end portion, and then heat treatment was performed at 190 ° C. for 1 hour.

The hardness of the conductive rubber layer obtained was Asker C
It was 54 ° and its resistance was 10 ⁴ ρ · cm.

Next, 30% of ISAF-grade carbon black was added.
A first coating layer having a resistance value of 2 × 10 ⁸ ρ · cm and a thickness of 200 μm was formed on the rubber layer by using a thermoplastic polyurethane dispersed by weight%, and N was further dispersed by 30% by weight of titanium oxide. A second coating layer having a resistance value of 3 × 10 ⁹ ρ · cm and a thickness of 5 μm was formed using methoxymethylated nylon.

The resistance value of the conductive roll manufactured as described above is 3 × 10 ⁵ Ω as a whole (measuring method: 1 cm width, H10k1 MΩ tester, 1000
V) After the roll was stored under the conditions of 15 ° C. and 10% RH for one week, the resistance value was 20 × 10 ⁶ Ω, but it could be sufficiently used.

[0032]

According to the present invention, since the electric resistance value hardly changes due to changes in the environment such as temperature and humidity, it is possible to provide a predetermined electric resistance value that is stable over a long period of time, and Has a large frictional resistance, so that a predetermined potential can be applied to the photosensitive drum and the recording medium, and the toner is hardly fused to the photosensitive drum, so that the photosensitive drum is not contaminated, and the development of the electrophotographic recording apparatus is prevented. A conductive roll suitable for use, charging, discharging, and transfer can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a conductive roll showing one embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 shaft 2 conductive rubber layer 3 first coating layer 4 second coating layer

Continuation of the front page (56) References JP-A-5-88509 (JP, A) JP-A-2-311871 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15 / 02 101 G03G 15/08 501 G03G 15/16 103 G03G 21/06 F16C 13/00

Claims (8)

(57) [Claims] 1. An electronic device comprising: a shaft having good conductivity; a conductive rubber layer provided on an outer periphery thereof; and a coating layer provided on an outer periphery of the rubber layer and having higher electric resistance than the rubber layer. In a conductive roll that imparts a potential of a predetermined polarity to a photoconductor or a recording medium of a photographic recording device while contacting them, the rubber layer is a rubber layer containing liquid polyisoprene rubber and solid butadiene rubber, and The coating layer includes a first coating layer formed on the rubber layer and a second coating layer formed on the first coating layer and having a higher resistance and a smaller thickness than the first coating layer. Conductive roll. 2. The liquid polyisoprene rubber has a temperature of 38 ° C.
2. The conductive roll according to claim 1, wherein the melt viscosity is 500 to 7000 cps and the average molecular weight (Mv) is 20000 to 60000. 3. The method according to claim 1, wherein the solid butadiene rubber is cis 1,4.
3. The conductive roll according to claim 1, wherein the conductive roll contains at least 90% of a structure. 4. The conductive roll according to claim 1, wherein the mixing ratio of the liquid polyisoprene rubber and the solid butadiene rubber is 10/90 to 50/50. 5. The method according to claim 1, wherein the first coating layer has a resistance value of 10 ⁶ to 10.
¹⁰ ρ · cm and a thickness of 30 to 500 μm.
5. The conductive roll according to any one of 4. 6. The conductive roll according to claim 1, wherein the first coating layer contains conductive carbon as a conductive agent. 7. The method according to claim 1, wherein the second coating layer has a resistance value of 10 ⁷ to 10.
The conductive roll according to any one of claims 1 to 6, wherein the conductive roll has a thickness of ¹¹ ρ · cm and a thickness of 10 µm or less. 8. The conductive roll according to claim 1, wherein the second coating layer contains titanium oxide.