JP2006235063A - Conductive rubber roller and transfer roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive rubber roller with reduced variation in the resistance value by the environment, and reduced resistance variation caused by power being applied for a long time, and free of staining properties. <P>SOLUTION: In a conductive rubber roller, a rubber layer is formed on a conductive core material. The rubber layer contains 35-90 mass parts of acrylonitrile-butadiene rubber; 50-9 mass parts of epichlorhydrin rubber; and 15-1 mass parts of polyethylene oxide-polypropylene oxide copolymer when the total of acrylonitrile-butadiene rubber, epichlorhydrin rubber, and polyethylene oxide-polypropylene oxide copolymer in the rubber material is 100 mass parts. The conductive rubber roller is made of the rubber composition of which content of the polyethylene oxide-polypropylene oxide copolymer is less than the content of epichlorhydrin rubber. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a conductive rubber roller and a transfer roller used in an image forming apparatus such as an electrophotographic copying apparatus, a printer, and an electrostatic recording apparatus.

  In many electrophotographic image forming apparatuses such as copying machines and printers, conductive rubber rollers such as a charging roller, a transfer roller, and a developing roller are used. Further, in many electrophotographic image forming apparatuses capable of color output, an intermediate transfer belt or a transfer conveyance belt is used. Generally, a transfer roller having a conductive rubber layer is disposed inside the intermediate transfer belt and the transfer conveyance belt to charge an image recording medium such as paper on the intermediate transfer belt or the transfer conveyance belt. is there. Conventionally, in order to impart conductivity to these rubber rollers, a method of adding a conductive filler such as carbon black or a method of blending an ion conductive rubber material such as acrylonitrile butadiene rubber or epichlorohydrin rubber can be cited (Patent Literature). 1).

  In the method of adding a conductive filler such as carbon black to impart conductivity to the rubber roller, the resistance value depends on the voltage value, and the resistance value varies depending on the lot. In view of this, the means using the latter ion-conductive acrylonitrile butadiene rubber, epichlorohydrin rubber, or a rubber material provided with an ion conductive agent, whose resistance value is relatively stable, has become the mainstream (for example, Patent Document 2).

However, these materials have a problem that the resistance value varies greatly depending on the environment. In particular, when trying to obtain a relatively low resistance value in a transfer roller for a color laser beam printer, it is necessary to increase the amount of rubber having a relatively low resistance value such as hydrin rubber, resulting in a resistance value environment. There is a problem that fluctuations become large. Further, when energized for a long time, there is a problem that the resistance fluctuation becomes large due to deterioration of acrylonitrile butadiene rubber, epichlorohydrin rubber or the like. Further, when an ionic conductive material is added, there is a problem that the conductive material bleeds out due to energization for a long time, and the photosensitive drum, the transfer belt, and the like are contaminated, and an image defect occurs. Therefore, due to the demand for higher image quality in future image forming apparatuses such as electrophotographic copying machines, printers, electrostatic recording devices, etc., contamination with reduced resistance values due to environmental changes and resistance values due to prolonged energization is reduced. There is a need for non-conductive conductive rubber rollers.
JP 2002-287456 A JP 2002-167519 A

  Therefore, in the present invention, in a conductive rubber roller such as a transfer roller, a charging roller, or a developing roller, the resistance value fluctuation due to the environment is reduced, the resistance fluctuation caused by energization for a long time is reduced, and there is no contamination. I will provide a.

  The present invention relates to a conductive rubber roller in which a rubber layer is formed on a conductive core material, wherein the rubber layer is a total of 100 of acrylonitrile butadiene rubber, epichlorohydrin rubber and polyethylene oxide-polypropylene oxide copolymer in the rubber material. In the case of mass parts, 35 to 90 parts by mass of the acrylonitrile butadiene rubber, 50 to 9 parts by mass of the epichlorohydrin rubber, 15 to 1 part by mass of the polyethylene oxide-polypropylene oxide copolymer, and This is achieved by the feature that the content of the polyethylene oxide-polypropylene oxide copolymer is less than the content of the epichlorohydrin rubber.

  The present invention is also achieved by the acrylonitrile butadiene rubber having a nitrile content of 15 to 43% by mass.

  The present invention is also achieved by the epichlorohydrin rubber which is an epichlorohydrin-ethylene oxide copolymer.

  The present invention is also achieved by the conductive rubber roller, wherein the rubber layer is formed of a foam.

  According to the present invention, the variation of the resistance value due to the environment is small, and the variation of the resistance value due to energization for a long time is small. Therefore, the conductive rubber roller of the present invention can be suitably used for a transfer roller used for image formation in electrophotographic technology.

  The present invention relates to a conductive rubber roller and a transfer roller in which a rubber layer is formed on a conductive core material, and the rubber layer is made of an acrylonitrile butadiene rubber, an epichlorohydrin rubber, a polyethylene oxide-polypropylene oxide copolymer in a rubber material. When the total is 100 parts by mass, the acrylonitrile butadiene rubber is contained in an amount of 35 to 90 parts by mass, the epichlorohydrin rubber is contained in an amount of 50 to 9 parts by mass, and the polyethylene oxide-polypropylene oxide copolymer is contained in an amount of 15 to 1 part by mass. And the content of the polyethylene oxide-polypropylene oxide copolymer is smaller than the content of the epichlorohydrin rubber.

  FIG. 2 shows an example in which the conductive rubber roller according to the present invention is used in an image forming apparatus. Here, the transfer roller disposed inside the transfer conveyance belt 20 will be described. The image forming apparatus shown in the figure is a color laser printer using an electrophotographic process cartridge, and the figure is a longitudinal sectional view showing a schematic configuration thereof. Further, the image forming apparatus shown in FIG. 1 is equipped with a transfer device having a transfer conveyance belt and a transfer roller disposed inside thereof.

  In FIG. 2, 1-Y, 1-M, 1-C, and 1-BK are drum-shaped electrophotographic photosensitive members (hereinafter referred to as photosensitive drums 1) as image bearing members, which are predetermined in the direction of the arrow. It is driven to rotate at a peripheral speed (process speed).

  Hereinafter, a process of forming a first color component image (for example, a yellow color component image) will be described.

  The photosensitive drum 1-Y is uniformly charged to a predetermined polarity and potential by the primary charger 2 during the rotation process, and then subjected to image exposure 3 by an image exposure means (not shown). In this way, an electrostatic latent image corresponding to the first color component image of the color image (in this example, the yellow color component image) is formed.

  Next, the electrostatic latent image is developed into a yellow component image by the first developing device (yellow color developing device 41). In this way, a first color (yellow) toner image is formed on the photosensitive drum 1-Y.

  Then, toner images of the second to fourth colors are formed on the photosensitive drums 1-M, 1-C, and 1-BK at a predetermined timing.

  On the other hand, the transfer / conveying belt 20 has substantially the same peripheral speed as the photosensitive drum 1 or a predetermined peripheral speed difference with respect to the photosensitive drum (in many cases, the transfer / conveying belt 20 is faster than the photosensitive drum 1) in the direction of the arrow. And is rotationally driven. Then, at a predetermined timing, the recording paper P is fed from the paper feed roller 11 to the transfer conveyance belt 20, and the recording paper P is transferred to the transfer conveyance belt 20 by the action of the adsorption bias applied to the adsorption roller 21 through the bias power supply 28. The recording paper P is conveyed along with the rotation of the transfer conveyance belt. The adsorption bias at this time is, for example, about −3 kV to +3 kV.

  When the recording paper P passes through the transfer nip (the part where the photosensitive drum 1 and the transfer roller 22 face each other via the transfer conveyance belt 20), a transfer bias is applied to the transfer roller 22 through the bias power supply 28. As a result, the toner image on the photosensitive member is transferred onto the recording paper P. That is, a yellow toner image that is a first color component, a magenta toner image that is a second color component, a cyan toner image that is a third color component, and finally a black toner that is a fourth color component. The toner images are sequentially laminated and transferred onto the recording paper P in the course of transporting the recording paper P. The transfer bias at this time is, for example, about −3 kV to +3 kV.

  The surface of the photosensitive drum 1 after the transfer of the toner image onto the recording paper P is cleaned by the photosensitive drum cleaning device 13.

  After the transfer of the toner image from the photosensitive drum 1, the recording paper P is conveyed directly below the corona neutralizer 24. An AC voltage of about 2 kVpp to 6 kVpp is applied to the corona neutralizer 24 from the bias power source 30, whereby the recording paper P is neutralized, the recording paper P is separated from the transfer conveyance belt 20, and the recording paper P is fixed. It is introduced into the vessel 15 and fixed by heating. Note that the corona neutralizer 24 is not always necessary, and the recording paper P may be separated from the transfer conveyance belt 20 without neutralization.

  When the toner comes into direct contact with the transfer / conveying belt 20, the transfer residual toner charging member (transfer residual toner charging member 9) on the belt that can come into contact with and separate from the belt is brought into contact with the belt at a predetermined timing. By applying a bias having a polarity opposite to that of the drum 1, the toner attached on the transfer conveyance belt 20 is charged to a polarity opposite to that of the photosensitive drum 1. At this time, the bias applied to the transfer residual toner charging member 9 is obtained by superimposing an AC voltage of about 1 kVpp to 3 kVpp on a DC voltage of about +10 to +1 kV, for example.

  The toner charged to the reverse polarity (+ polarity) is electrostatically transferred to the photosensitive drum 1 at and near the contact portion with the photosensitive drum 1, thereby cleaning the transfer conveyance belt 20, and the next image. Prepare for formation.

  The above is the outline of the operation of the image forming apparatus using the transfer conveyance belt and the four photosensitive members.

  A conductive rubber roller (FIG. 1) demonstrating the present invention was produced as follows.

[Conductive rubber roller]
The rubber composition contains 35 to 90 parts by mass of the acrylonitrile butadiene rubber and 50 to 9 parts of the epichlorohydrin rubber when the total of acrylonitrile butadiene rubber, epichlorohydrin rubber and polyethylene oxide-polypropylene oxide copolymer is 100 parts by mass. A mixture containing 15 parts by mass of the polyethylene oxide-polypropylene oxide copolymer, and a content of the polyethylene oxide-polypropylene oxide copolymer is less than that of the epichlorohydrin rubber. This is mixed with a filler such as carbon black, a vulcanizing agent such as sulfur, a vulcanization accelerator, and a foaming agent. The acrylonitrile butadiene rubber has a nitrile content of 15 to 43% by mass, and the epichlorohydrin rubber is a terpolymer of epichlorohydrin-ethylene oxide-allyl glycidyl ether.

  In the above, when the amount of acrylonitrile butadiene rubber is 35 parts by mass or less, the resistance value varies greatly depending on the environment, which causes a problem that it is not suitable for practical use. When the amount of acrylonitrile butadiene rubber is 90 parts by mass or more, there arises a problem that the resistance value fluctuates greatly due to energization for a long time, and in the worst case, a crack occurs on the roller surface. Moreover, when epichlorohydrin rubber is 50 mass parts or more, the problem that the environmental dependence of resistance value will become large arises. When the epichlorohydrin rubber is 9 parts by mass or less, the problem that the resistance value fluctuates greatly due to energization for a long time tends to occur. When the polyethylene oxide-polypropylene oxide copolymer is 15 parts by mass or more, there arises a problem that the resistance value fluctuates too much due to the environment. When the polyethylene oxide-polypropylene oxide copolymer is 1 part by mass or less, there arises a problem that the resistance value fluctuates greatly due to energization for a long time. In addition, when the content of polyethylene oxide-polypropylene oxide copolymer is larger than the content of epichlorohydrin rubber, the polyethylene oxide-polypropylene oxide copolymer tends to bleed out, and the inside of the transfer conveyance belt can be used as a transfer roller. This causes the problem of contaminating etc.

  The acrylonitrile butadiene rubber is not particularly limited, but the nitrile content is usually in the range of 15 to 43% by mass, preferably 35 to 15% by mass, more preferably 24 to 15% by mass. Furthermore, a low viscosity type having good extrudability and the like is preferable.

  The epichlorohydrin rubber is not particularly limited, but an epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer is preferable. The polymerization ratio of the epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer is not particularly limited, and the copolymerization ratio of epichlorohydrin / ethylene oxide / allyl glycidyl ether is usually 20 to 100 mol% / 0 to 75 mol. % / 0 to 10 mol%, preferably 20 to 70 mol% / 20 to 75 mol% / 2 to 10 mol%, more preferably 20 to 60/40 to 75/2 to 10 mol%.

  The polyethylene oxide-polypropylene oxide copolymer is not particularly limited, but the copolymerization ratio of polyethylene oxide and polypropylene oxide is 50 to 95 mol% / 5 to 50 mol%, preferably 70 to 95 mol% / 5 to 5. It is 30 mol%, More preferably, it is the range of 85-95 mol% / 5-15 mol%.

  After extruding the rubber composition using an extruder (not shown) to obtain an unvulcanized tube-shaped conductive rubber molded product, the tube is vulcanized at 160 ° C. for 30 minutes in a vulcanization can. A conductive rubber molded product was prepared, and then a φ6 mm conductive core material was press-fitted into the inner diameter portion of the tube-shaped conductive rubber molded product to obtain a roller-shaped molded product. This molded body is set in a polishing machine (not shown) equipped with a polishing grindstone GC80, polished as a polishing condition so that the outer diameter is 12 to 14 mm at a rotational speed of 2000 RPM and a feed speed of 500 m / min. A rubber roller was produced.

  In addition, the material used by each Example and the comparative example is as follows.

Acrylonitrile butadiene rubber
[Product name: Nipol DN401LL Nitrile content 18% by mass Nippon Zeon Co., Ltd.]
Epichlorohydrin rubber
[Product Name: Epion ON-301 Daiso Corporation]
Polyethylene oxide-polypropylene oxide copolymer
[Product Name: ZSN8100 Nippon Zeon Co., Ltd.]
(Measurement method of electrical resistance and environmental variation of conductive rubber roller)
The electric resistance of the conductive rubber roller is such that a load of 4.9 N on one side is applied to the shaft body of the conductive rubber roller, and it is pressed against a stainless steel drum having an outer diameter of 30 mm and rotated in the rotated state. The voltage of 500V was applied between and measured. This measurement was performed after being left for 48 hours in each environment of L / L (15 ° C. × 10% RH), N / N (23 ° C. × 55% RH), and H / H (35 ° C. × 85% RH). did. The amount of environmental fluctuation is expressed in digits of the difference in resistance value between L / L and H / H. The fluctuation amount is preferably 1.8 digits or less.

  Here, the difference between the initial resistance value and the resistance value after the endurance was expressed in terms of the number of digits, and was defined as the energization variation. It is determined that the smaller this is, the better the energization durability of the transfer roller. The fluctuation amount is preferably 0.7 digits or less.

(Conductive rubber roller energization test method)
The energization durability test of the conductive rubber roller was conducted for 300 hours using a laser beam printer (made by Color Laser Jet 4600 HP) in a 15 ° C. × 10% environment. Thereafter, the roller resistance was measured after being left for 1 hour in an L / L environment. Here, the difference between the initial resistance value represented by the number of digits and the resistance value after durability represented by the number of digits was defined as the energization fluctuation amount. It can be said that the smaller this is, the better the current-carrying durability of the transfer roller. The fluctuation amount is preferably 0.7 digits or less.

  Here, the surface of the transfer / conveying belt that had been energized for 300 hours was markedly contaminated if it was markedly contaminated by bleeding out from the transfer roller.

(Evaluation method for contamination of conductive rubber roller)
The conductive rubber roller was evaluated for contamination by conducting a continuous energization test for 72 hours using a laser beam printer (made by Color Laser Jet 4600 HP) in a room temperature and humidity environment. The thing with the remarkable stain | pollution | contamination resulting from out was made into the contamination property.
[Example]
Examples 1 to 6 are examples of conductive rubber rollers in which a rubber layer is formed on a conductive core material, in which the rubber layer is an acrylonitrile butadiene rubber, an epichlorohydrin rubber, and a polyethylene oxide-polypropylene oxide copolymer in a rubber material. When the total amount is 100 parts by mass, the acrylonitrile butadiene rubber is contained in an amount of 35 to 90 parts by mass, the epichlorohydrin rubber is contained in an amount of 50 to 9 parts by mass, and the polyethylene oxide-polypropylene oxide copolymer is contained in an amount of 15 to 1 part by mass. It is an electroconductive rubber roller of the present invention containing.

  Example 1 contained a polyethylene oxide-polypropylene oxide copolymer and showed good values for both environmental fluctuation and durability fluctuation. In addition, since the content of the polyethylene oxide-polypropylene oxide copolymer is less than the content of the epichlorohydrin rubber, it was possible to obtain a result that there was no problem with contamination inside the transfer conveyance belt due to bleed out from the transfer roller. .

  Furthermore, since Example 2 contained the polyethylene oxide-polypropylene oxide copolymer and contained a large amount of the acrylonitrile butadiene rubber, it was possible to obtain a good value for the environmental fluctuation of the resistance value.

  Examples 3 and 4 are conductive rubber rollers of the present invention containing an equal amount of epichlorohydrin rubber and polyethylene oxide-polypropylene oxide copolymer, and good values were obtained along with environmental fluctuation and durability fluctuation. Since an equivalent amount of epichlorohydrin rubber having good compatibility with the polyethylene oxide-polypropylene oxide was contained, the contamination inside the transfer conveyance belt caused by bleed out from the transfer roller could be obtained without any problem.

  Also in Example 5, a polyethylene oxide-polypropylene oxide copolymer was contained, and good results were obtained in terms of environmental fluctuation, durability fluctuation, and contamination.

Example 6 contained a polyethylene oxide-polypropylene oxide copolymer, and good results were obtained in both environmental fluctuation and contamination. Since a large amount of epichlorohydrin rubber was contained, a good value was obtained in the durability fluctuation of the resistance value.
[Comparative example]
As comparative examples, when the acrylonitrile butadiene rubber is contained in an amount of 90 to 35 parts by mass, the epichlorohydrin rubber is contained in an amount of 50 to 9 parts by mass, and the polyethylene oxide-polypropylene oxide copolymer Several coalesces of 15 to 1 parts by mass were selected as comparative examples.

  In Comparative Example 1, since the polyethylene oxide-polypropylene oxide copolymer was not contained, the resistance value durability fluctuation was 0.8 digits, which was inappropriate.

  In Comparative Example 2, since the epichlorohydrin rubber is not included, the environmental fluctuation of the resistance value is as large as 0.8 digits, and furthermore, the transfer conveyance belt is significantly soiled due to the polyethylene oxide-polypropylene oxide bleed out from the transfer roller. there were.

  In Comparative Example 3, since the acrylonitrile butadiene rubber was not contained, the environmental dependency of the resistance value was 2.1 digits, which was inappropriate.

  In Comparative Example 4, since the amount of polyethylene oxide-polypropylene oxide was as large as 20 parts by mass, the environmental dependency of the resistance value was as large as 2.0 digits, which was inappropriate.

  In Comparative Example 5, the content of the epichlorohydrin rubber was as small as 5 parts by mass, and the content of the polyethylene oxide-polypropylene oxide copolymer was larger than the content of the epichlorohydrin rubber, so that the polyethylene oxide-polypropylene from the transfer roller Belt contamination due to bleedout of the oxide copolymer occurred and was not suitable.

  In Comparative Example 6, since the epichlorohydrin was contained as much as 55 parts by mass, the environmental dependency of the resistance value was not suitable.

  In Comparative Example 7, since the amount of the acrylonitrile butadiene rubber was as large as 95 parts by mass, a crack occurred on the roller surface during energization, and the energization test was impossible.

  From this result, in the conductive rubber roller and the transfer roller in which the rubber layer is formed on the conductive core material, the rubber layer is a total of acrylonitrile butadiene rubber, epichlorohydrin rubber and polyethylene oxide-polypropylene oxide copolymer in the rubber material. When the acrylonitrile butadiene rubber is 35 to 90 parts by weight, and the epichlorohydrin rubber is 50 to 9 parts by weight, and the polyethylene oxide-polypropylene oxide copolymer is 1 to 15 parts by weight, It is possible to obtain a conductive rubber roller in which fluctuations in resistance due to the environment are reduced, resistance fluctuations caused by energization for a long time are reduced, and there is no contamination. The results are shown in Table 1.

  In the case of the range of the comparative example, the resistance value varies greatly depending on the environment. Alternatively, it can be seen that the resistance fluctuates due to energization for a long time, or that the transfer conveyance belt or the like is contaminated due to bleeding out from the transfer roller. The results are shown in Table 2.

  In the conductive rubber roller of the present invention, the variation of the resistance value due to the environment is small, and the variation of the resistance value due to energization for a long time is small. Therefore, the conductive rubber roller can be suitably used for a transfer roller used for image formation in electrophotographic technology.

1 is an overall view of a transfer roller according to the present invention. 1 is a schematic view of an image forming apparatus according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 1-Y Yellow color photosensitive drum 1-M Magenta color photosensitive drum 1-C Cyan color photosensitive drum 1-BK Black color photosensitive drum 2 Primary charger 3 Image exposure 9 Transfer residual toner charging member 10 Transfer material guide 11 Paper feeding roller 13 Photosensitive drum cleaning device 15 Fixing device 20 Transfer conveyance belt 21 Adsorption roller 22 Transfer roller 221 Core metal 222 Elastic layer 24 Corona static eliminator 27 Bias power supply 28 Bias power supply 41 Yellow color developer 42 Magenta color developer 43 Cyan Color developer 44 Black color developer P Recording paper

Claims (6)

  In the conductive rubber roller in which the rubber layer is molded on the conductive core material, the rubber layer is 100 parts by mass of the total of the acrylonitrile butadiene rubber, epichlorohydrin rubber and polyethylene oxide-polypropylene oxide copolymer in the rubber material. The acrylonitrile butadiene rubber is 35 to 90 parts by mass, the epichlorohydrin rubber is 50 to 9 parts by mass, and the polyethylene oxide-polypropylene oxide copolymer is 15 to 1 part by mass, and A conductive rubber roller, wherein the content of the polyethylene oxide-polypropylene oxide copolymer is less than the content of the epichlorohydrin rubber.   The conductive rubber roller according to claim 1, wherein the acrylonitrile butadiene rubber has a nitrile content of 15 to 43% by mass.   3. The conductive rubber roller according to claim 1, wherein the epichlorohydrin rubber is an epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer.   The conductive rubber roller according to claim 1, wherein the rubber layer is formed of a foam.   5. A transfer roller, wherein a transfer roller of a transfer device mounted on an electrophotographic apparatus is the conductive rubber roller according to claim 1.   5. A transfer roller according to claim 1, wherein the transfer roller disposed inside the intermediate transfer belt or the transfer conveyance belt mounted on the electrophotographic apparatus is the conductive rubber roller according to claim 1.